Ic-trosa point-to-multipoint optical network system

ABSTRACT

An IC-TROSA point-to-multipoint optical network system includes a point-to-multipoint optical network that is coupled to subscriber devices, and that is coupled to a hub device via a hub IC-TROSA device included in a hub coherent optical transceiver device coupled to the hub device. The hub IC-TROSA device includes a quadrature optical modulator subsystem, and an optical directional coupler device in the quadrature optical modulator subsystem provides a first transmit connection and a second transmit connection to the point-to-multipoint optical network. The optical directional coupler device receives first optical signals from the quadrature optical modulator subsystem and transmits them via the first transmit connection to a first subset of the subscriber devices via the point-to-multipoint optical network, and receives second optical signals from the quadrature optical modulator subsystem and transmits them via the second transmit connection to a second subset of the subscriber devices via the point-to-multipoint optical network.

BACKGROUND

The present disclosure relates generally to information handlingsystems, and more particularly to an Integrated CoherentTransmit-Receive Optical Sub-Assembly (IC-TROSA) device for transmittingdata between information handling systems connected via apoint-to-multipoint optical network.

As the value and use of information continues to increase, individualsand businesses seek additional ways to process and store information.One option available to users is information handling systems. Aninformation handling system generally processes, compiles, stores,and/or communicates information or data for business, personal, or otherpurposes thereby allowing users to take advantage of the value of theinformation. Because technology and information handling needs andrequirements vary between different users or applications, informationhandling systems may also vary regarding what information is handled,how the information is handled, how much information is processed,stored, or communicated, and how quickly and efficiently the informationmay be processed, stored, or communicated. The variations in informationhandling systems allow for information handling systems to be general orconfigured for a specific user or specific use such as financialtransaction processing, airline reservations, enterprise data storage,or global communications. In addition, information handling systems mayinclude a variety of hardware and software components that may beconfigured to process, store, and communicate information and mayinclude one or more computer systems, data storage systems, andnetworking systems.

Information handling systems such as server devices, storage systems,and/or other computing devices known in the art, are sometimes coupledtogether using optical networks. In many situations, apoint-to-multipoint optical network may be provided to allow, forexample, a hub device (e.g., provided by a networking device (e.g., aswitch device or router device) and/or other computing devices thatwould be apparent to one of skill in the art in possession of thepresent disclosure) to transmit and receive data via optical signalswith subscriber devices (e.g., provided by server devices, networkingdevices (e.g., switch devices or router devices), subscriber gatewaydevices, storage systems, and/or other computing devices that would beapparent to one of skill in the art in possession of the presentdisclosure). Conventionally, Passive Optical Networks (PONs) have beenprovided for such point-to-multipoint optical networks (e.g., PONs havebeen relatively widely deployed to provide opticalfiber-to-homeservices), and operate based on Intensity Modulation and DirectDetection (IM/DD) optical communication technologies that distinguishoptical signals from different subscriber devices at the hub devicebased on a Time-Division Multiple Access (TDMA) scheme. However, as thedesire to transmit optical signals at higher speeds and longer distancesincreases, point-to-multipoint optical networks will shift to theutilization of coherent optical communication technologies, which haveconventionally been utilized in point-to-point optical communicationsbetween discrete devices at each end of the optical link.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, coherent optical communication technologies operateto modulate the amplitude and phase of light transmitted via opticalfibers across multiple polarizations, which enables the transmission ofmore data relative to IM/DD optical communication technologies, and whencombined with Digital Signal Processing (DSP) techniques at thetransmitter and receiver, achieves higher bitrates, greater linkbudgets, greater degrees of flexibility, simpler photonic line systems,and increased optical performance relative to IM/DD opticalcommunication technologies. However, coherent optical communicationtechnologies have not been widely deployed in point-to-multipointoptical networks as of yet.

The conventional implementation of coherent optical communicationtechnologies for point-to-multipoint optical networks provides a hubcoherent optical transceiver device coupled to the hub device, arespective subscriber coherent optical transceiver device coupled toeach subscriber device, and a point-to-multipoint optical networkconnecting the hub coherent optical transceiver device to each of thesubscriber coherent optical transceiver devices. Furthermore, each ofthe hub coherent optical transceiver device and the subscriber coherentoptical transceiver devices may include a DSP device, an IntegratedCoherent Transmit-Receive Optical Sub-Assembly (IC-TROSA) device, and anIntegrated Tunable Laser Assembly (ITLA) device or devices. However, theinventor of the present disclosure has discovered that the conventionalconfiguration of the IC-TROSA devices in hub coherent opticaltransceiver devices suffer from issues that limit the efficiency ofoptical signal transmission.

For example, conventional IC-TROSA devices utilize 2×1 single-modeY-junction optical waveguides within their quadrature optical modulatordevices, and in some cases with their 90-degree optical hybrid mixerdevices as well. As will be appreciated by one of skill in the art inpossession of the present disclosure, when light traverses a 2×1single-mode Y-junction optical waveguide from the two-input side to thesingle-output side, only half of the light power input is transmitted atthe output, with the other half of the light power input radiated fromthe 2×1 single-mode Y-junction optical waveguide as “waste light”. Aswill be appreciated by one of skill in the art in possession of thepresent disclosure, the reduction in light power via the 2×1 single-modeY-junction optical waveguides utilized in conventional IC-TROSA deviceslimits the distance that optical signals may be transmitted by the hubdevice to any particular number of subscriber devices, or reduces thenumber of subscriber devices to which a hub device may transmit opticalsignals for any particular distance.

Accordingly, it would be desirable to provide an IC-TROSApoint-to-multipoint optical network system that addresses the issuesdiscussed above.

SUMMARY

According to one embodiment, a hub coherent optical transceiver devicecomprises: a quadrature optical modulator subsystem; a first opticaldirectional coupler device that is included in the quadrature opticalmodulator subsystem; a first transmit connection provided by the firstoptical direction coupler device, wherein the first optical directionalcoupler device is configured to receive first optical signals from thequadrature optical modulator subsystem and transmit the first opticalsignals via the first transmit connection to a first subset of theplurality of subscriber devices via the point-to-multipoint opticalnetwork; and a second transmit connection provided by the first opticaldirection coupler device, wherein the first optical directional couplerdevice is configured to receive second optical signals from thequadrature optical modulator subsystem and transmit the second opticalsignals via the second transmit connection to a second subset of theplurality of subscriber devices via the point-to-multipoint opticalnetwork.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view illustrating an embodiment of an InformationHandling System (IHS).

FIG. 2 is a schematic view illustrating an embodiment of a hub coherentoptical transceiver device provided according to the teachings of thepresent disclosure.

FIG. 3 is a schematic view illustrating an embodiment of a subscribercoherent optical transceiver device provided according to the teachingsof the present disclosure.

FIG. 4 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 .

FIG. 5 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 .

FIG. 6 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 coupled to a hub device,as well as to a plurality of the subscriber coherent optical transceiverdevices of FIG. 3 (which are each coupled to subscriber devices) via aplurality of networks.

FIG. 7 is a perspective view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 being coupled to a hubdevice.

FIG. 8 is a schematic view illustrating an embodiment of a conventionalIC-TROSA device.

FIG. 9 is a schematic view illustrating an embodiment of theconventional IC-TROSA device of FIG. 8 coupled to subscriber devices viaa network.

FIG. 10 is a schematic view illustrating an embodiment of the operationof a 2×1 single-mode Y-junction optical waveguide included in theconventional IC-TROSA device of FIG. 8 .

FIG. 11 is a schematic view illustrating an embodiment of the operationof the conventional IC-TROSA device of FIG. 8 .

FIG. 12 is a schematic view illustrating an embodiment of the operationof the network of FIG. 9 .

FIG. 13 is a flow chart illustrating an embodiment of a method fortransmitting data via a point-to-multipoint optical network.

FIG. 14A is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 operating during themethod of FIG. 13 .

FIG. 14B is a schematic view illustrating an embodiment of a quadratureoptical modulator subsystem provided according to the teachings of thepresent disclosure in the hub coherent optical transceiver device ofFIG. 4 and operating during the method of FIG. 13 .

FIG. 15 is a schematic view illustrating an embodiment of the operationof the conventional quadrature optical modulator device in aconventional IC-TROSA device of FIG. 8 .

FIG. 16 is a schematic view illustrating an embodiment of the operationof an optical directional coupler device.

FIG. 17A is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 6 transmitting opticalsignals to a subscriber coherent optical transceiver device via one ofthe plurality of networks during the method of FIG. 13 .

FIG. 17B is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 6 transmitting opticalsignals to a subscriber coherent optical transceiver device via one ofthe plurality of networks during the method of FIG. 13 .

FIG. 18 is a schematic view illustrating an embodiment of the subscribercoherent optical transceiver device of FIG. 3 operating during themethod of FIG. 13 .

FIG. 19 is a schematic view illustrating an embodiment of the operationof the conventional coherent optical receive/90-degree optical hybridmixer device in a conventional IC-TROSA device of FIG. 8 .

FIG. 20 is a flow chart illustrating an embodiment of a method fortransmitting data via a point-to-multipoint optical network.

FIG. 21 is a schematic view illustrating an embodiment of the subscribercoherent optical transceiver device of FIG. 3 operating during themethod of FIG. 20 .

FIG. 22 is a schematic view illustrating an embodiment of the subscribercoherent optical transceiver devices of FIG. 6 transmitting opticalsignals to the hub coherent optical transceiver device via each of theplurality of networks during the method of FIG. 20 .

FIG. 23 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 operating during themethod of FIG. 20 .

FIG. 24 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 4 operating during themethod of FIG. 20 .

FIG. 25 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 5 operating during themethod of FIG. 20 .

FIG. 26 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 coupled to a plurality ofthe subscriber coherent optical transceiver devices of FIG. 3 via aplurality of networks.

FIG. 27 is a schematic view illustrating an embodiment of theconventional IC-TROSA device of FIG. 8 coupled to a plurality of thesubscriber devices via a network.

FIG. 28 is a schematic view illustrating an embodiment of the hubcoherent optical transceiver device of FIG. 2 coupled to a plurality ofthe subscriber coherent optical transceiver devices of FIG. 3 via aplurality of networks.

FIG. 29 is a schematic view illustrating an embodiment of a quadratureoptical modulator subsystem provided according to the teachings of thepresent disclosure in the hub IC-TROSA device provided according to theteachings of the present disclosure.

FIG. 30 is a schematic view illustrating an embodiment of a quadratureoptical modulator subsystem provided according to the teachings of thepresent disclosure in the hub IC-TROSA device provided according to theteachings of the present disclosure.

DETAILED DESCRIPTION

For purposes of this disclosure, an information handling system mayinclude any instrumentality or aggregate of instrumentalities operableto compute, calculate, determine, classify, process, transmit, receive,retrieve, originate, switch, store, display, communicate, manifest,detect, record, reproduce, handle, or utilize any form of information,intelligence, or data for business, scientific, control, or otherpurposes. For example, an information handling system may be a personalcomputer (e.g., desktop or laptop), tablet computer, mobile device(e.g., personal digital assistant (PDA) or smart phone), server (e.g.,blade server or rack server), a network storage device, or any othersuitable device and may vary in size, shape, performance, functionality,and price. The information handling system may include random accessmemory (RAM), one or more processing resources such as a centralprocessing unit (CPU) or hardware or software control logic, ROM, and/orother types of nonvolatile memory. Additional components of theinformation handling system may include one or more disk drives, one ormore network ports for communicating with external devices as well asvarious input and output (I/O) devices, such as a keyboard, a mouse,touchscreen and/or a video display. The information handling system mayalso include one or more buses operable to transmit communicationsbetween the various hardware components.

In one embodiment, IHS 100, FIG. 1 , includes a processor 102, which isconnected to a bus 104. Bus 104 serves as a connection between processor102 and other components of IHS 100. An input device 106 is coupled toprocessor 102 to provide input to processor 102. Examples of inputdevices may include keyboards, touchscreens, pointing devices such asmouses, trackballs, and trackpads, and/or a variety of other inputdevices known in the art. Programs and data are stored on a mass storagedevice 108, which is coupled to processor 102. Examples of mass storagedevices may include hard discs, optical disks, magneto-optical discs,solid-state storage devices, and/or a variety of other mass storagedevices known in the art. IHS 100 further includes a display 110, whichis coupled to processor 102 by a video controller 112. A system memory114 is coupled to processor 102 to provide the processor with faststorage to facilitate execution of computer programs by processor 102.Examples of system memory may include random access memory (RAM) devicessuch as dynamic RAM (DRAM), synchronous DRAM (SDRAM), solid state memorydevices, and/or a variety of other memory devices known in the art. Inan embodiment, a chassis 116 houses some or all of the components of IHS100. It should be understood that other buses and intermediate circuitscan be deployed between the components described above and processor 102to facilitate interconnection between the components and the processor102.

Referring now to FIG. 2 , an embodiment of a hub coherent opticaltransceiver device 200 is illustrated. In the embodiments illustratedand described below, the hub coherent optical transceiver device 200 isillustrated and described as being provided by a pluggable module suchas those described in the Quad Small Form-factor PluggableDouble-Density (QSFP-DD) or Octal Small Form-factor Pluggable (OSFP)Multi-Source Agreements (MSAs), although other pluggable moduleform-factors will fall within the scope of the present disclosure aswell. Furthermore, while illustrated and described as being provided bya pluggable module, one of skill in the art in possession of the presentdisclosure will appreciate that the hub coherent optical transceiverdevice 200 may be integrated into the hub devices discussed below whileremaining within the scope of the present disclosure as well. In theillustrated embodiment, the hub coherent optical transceiver device 200includes a chassis 202 that houses the components of the hub coherentoptical transceiver device 200, only some of which are illustrated anddiscussed below.

For example, the chassis 202 may house a processing system (notillustrated, but which may include the processor 102 discussed abovewith reference to FIG. 1 ) and a memory system (not illustrated, butwhich may include the memory 114 discussed above with reference to FIG.1 ) that is coupled to the processing system and that includesinstructions that, when executed by the processing system, cause theprocessing system to provide a hub signal processing engine 204 that isconfigured to perform the functionality of the hub signal processingengines, hub signal processing subsystems, and/or hub coherent opticaltransceiver devices discussed below. In a specific example, the hubsignal processing engine 204 may perform a variety of Digital SignalProcessing (DSP) operations including encoding data streams intotime-domain waveforms to drive coherent transmitters, decodingtime-domain electrical waveforms measured at different coherentreceivers into data streams, optical phase recovery and locking,polarization tracking and demultiplexing, chromatic dispersioncompensation, polarization mode dispersion compensation, spectralshaping, forward error correction encoding and decoding, as well as avariety of other operations that would be apparent to one of skill inthe art in possession of the present disclosure.

The chassis 202 also includes a hub device connector 206 (e.g., amulti-pin electrical connector), and the hub signal processing engine204 (e.g., the processing system that provides the hub signal processingengine 204) is coupled to the hub device connector 206 via a data inputconnection 204 a and a data output connection 204 b. In a specificexample, the hub device connector 206 may be provided by a QSFP-DD orOSFP connector, and/or other hub device connectors that would beapparent to one of skill in the art in possession of the presentdisclosure. The chassis 202 may also include a hub Integrated CoherentTransmit-Receive Optical Sub-Assembly (IC-TROSA) device 208 that isconfigured according to the teachings of the present disclosure,discussed in further detail below, and the hub signal processing engine204 (e.g., the processing system that provides the hub signal processingengine 204) is coupled to the hub IC-TROSA device 208 via a data outputconnection 204 c and a data input connection 204 d.

The chassis 202 also includes a first hub optical network connector 210(e.g., a duplex optical connector) that is configured to couple to anoptical connector on an optical cable, and the hub IC-TROSA device 208is coupled to the first hub optical network connector 210 via a firstoptical transmit connection 210 a and first optical receive connection210 b. The chassis 202 also includes a second hub optical networkconnector 212 (e.g., a duplex optical connector) that is configured tocouple to an optical connector on an optical cable, and the hub IC-TROSAdevice 208 is coupled to the second hub optical network connector 212via a second optical transmit connection 212 a and second opticalreceive connection 212 b. The chassis 202 also includes a hub IntegratedTunable Laser Assembly (ITLA) device 214 that is coupled to the hubIC-TROSA device 208. As discussed below, the hub ITLA device 214 may beconfigured to provide light (e.g., highly-coherent, narrow-linewidthlaser light waves) that is discussed below as being described by complexelectrical fields referred to as a receiver local oscillator electricalfield E_(L) and a transmitter laser source electrical field E_(st), andone of skill in the art in possession of the present disclosure willrecognize that the receiver local oscillator electrical field E_(L) andthe transmitter laser source electrical field E_(st) may be provided atthe same wavelength (e.g., from a single ITLA device) or differentwavelengths (e.g., from multiple ITLA devices).

Furthermore, one of skill in the art in possession of the presentdisclosure will appreciate that a single hub ITLA device may provideboth the receiver local oscillator electrical field E_(L) and thetransmitter laser source electrical field E_(St), or separate hub ITLAdevices may provide the receiver local oscillator electrical field E_(L)and the transmitter laser source electrical field E_(St), whileremaining within the scope of the present disclosure. Further still,while illustrated as a separate device, one of skill in the art inpossession of the present disclosure will recognize that the hub ITLAdevice 214 may be integrated into the hub IC-TROSA device 208 whileremaining within the scope of the present disclosure as well. However,while a specific hub coherent optical transceiver device 200 has beenillustrated and described, one of skill in the art in possession of thepresent disclosure will recognize that hub coherent optical transceiverdevice devices (or other devices operating according to the teachings ofthe present disclosure in a manner similar to that described below forthe hub coherent optical transceiver device 200) may include a varietyof components and/or component configurations for providing conventionalhub coherent optical transceiver device functionality, as well as thefunctionality discussed below, while remaining within the scope of thepresent disclosure as well.

Referring now to FIG. 3 , an embodiment of a subscriber coherent opticaltransceiver device 300 is illustrated. In the embodiments illustratedand described below, the subscriber coherent optical transceiver device300 is illustrated and described as being provided by a pluggable modulesuch as those described in the QSFP or OSFP MSAs, although otherpluggable module form-factors will fall within the scope of the presentdisclosure as well. Furthermore, while illustrated and described asbeing provided by a pluggable module, one of skill in the art inpossession of the present disclosure will appreciate that the subscribercoherent optical transceiver device 300 may be integrated into thesubscriber devices discussed below while remaining within the scope ofthe present disclosure as well. In the illustrated embodiment, thesubscriber coherent optical transceiver device 300 includes a chassis302 that houses the components of the subscriber coherent opticaltransceiver device 300, only some of which are illustrated and discussedbelow.

For example, the chassis 302 may house a processing system (notillustrated, but which may include the processor 102 discussed abovewith reference to FIG. 1 ) and a memory system (not illustrated, butwhich may include the memory 114 discussed above with reference to FIG.1 ) that is coupled to the processing system and that includesinstructions that, when executed by the processing system, cause theprocessing system to provide a subscriber signal processing engine 304that is configured to perform the functionality of the subscriber signalprocessing engines, subscriber signal processing subsystems, and/orsubscriber coherent optical transceiver devices discussed below. In aspecific example, the subscriber signal processing engine 304 mayperform a variety of DSP operations including encoding data streams intotime-domain waveforms to drive coherent transmitters, decodingtime-domain electrical waveforms measured at different coherentreceivers into data streams, optical phase locking, polarizationtracking and demultiplexing, chromatic dispersion compensation,polarization mode dispersion compensation, spectral shaping, forwarderror correction encoding and decoding, as well as a variety of otheroperations that would be apparent to one of skill in the art inpossession of the present disclosure.

As discussed below, the subscriber signal processing engine 304 may beconfigured to perform signal processing operations that enable it todecode signals received from the hub coherent optical transceiver device200. In an embodiment, the subscriber coherent optical transceiverdevice 300 may be a conventional subscriber coherent optical transceiverdevice with the exception of the subscriber signal processing engine 304that may be configured to perform first signal processing operations onfirst optical signals received from the hub coherent optical transceiverdevice 200, and second signal processing operations on second opticalsignals received from the hub coherent optical transceiver device 200.For example, the first signal processing operations discussed above maybe conventional signal processing operations that are configured todecode conventional optical signals from the hub coherent opticaltransceiver device 200, while the second signal processing operationsmay be configured to decode optical signals from the hub coherentoptical transceiver device 200 that are generated according to theteachings of the present disclosure.

In a specific example in which the subscriber coherent opticaltransceiver device 300 is a conventional subscriber coherent opticaltransceiver device, the subscriber signal processing engine 304 may beupgraded, updated, and/or otherwise configured by the subscribercoherent optical transceiver device 300 receiving (e.g., via thepoint-to-multipoint optical network, via an out-of-band channel, etc.),a subscriber signal processing engine update, and processing thatsubscriber signal processing engine update (e.g., performing asoftware/firmware update) in order to configure the subscriber coherentoptical transceiver device to perform the second signal processingoperations when appropriate. However, while the subscriber coherentoptical transceiver device 300 is described as a conventional subscribercoherent optical transceiver device that has its software/firmwareupgraded/updated/configured to enable the functionality of the presentdisclosure, one of skill in the art in possession of the presentdisclosure will appreciate how embodiments in which the subscribercoherent optical transceiver device 300 is configured similarly to thehub coherent optical transceiver device 200 (e.g., with the subscriberIC-TROSA device discussed below configured similarly to the hub IC-TROSAdevice 208 discussed above, but operating using only one of the opticaltransmit connections and one of the optical receive connections,discussed below) will fall within the scope of the present disclosure aswell.

The chassis 302 also includes a subscriber device connector 306 (e.g.,an electrical connector), and the subscriber signal processing engine304 (e.g., the processing system that provides the subscriber signalprocessing engine 304) is coupled to the subscriber device connector 306via a data input connection 304 a and a data output connection 304 b(e.g., a plurality of parallel data connections that provide the datainput connection 304 a and the data output connection 304 b and thateach carry a distinct data stream). In a specific example, thesubscriber device connector 306 may be provided by a QSFP or OSFPconnector, and/or other subscriber device connectors that would beapparent to one of skill in the art in possession of the presentdisclosure. The chassis 302 may also include a subscriber IC-TROSAdevice 308, and the subscriber signal processing engine 304 (e.g., theprocessing system that provides the subscriber signal processing engine304) is coupled to the subscriber IC-TROSA device 308 via a data outputconnection 304 c and a data input connection 304 d (e.g., a plurality ofparallel data connections that provide the data output connection 304 cand the data input connection 304 d and that each carry a distinct datastream), with the electrical data output connection 304 c including oneor more optical modulator driver circuits, and the electrical data inputconnection 304 d including one or more electrical amplifier circuits..As discussed above, the subscriber IC-TROSA device 308 may be providedby a conventional subscriber IC-TROSA device, with the subscriber signalprocessing engine 304 configured to enable the functionality of thepresent disclosure via signal processing operations performed on signalsreceived from the hub coherent optical transceiver device 200. However,one of skill in the art in possession of the present disclosure willappreciate how embodiments in which the subscriber IC-TROSA device 308is configured similarly to the hub IC-TROSA device 208 discussed abovewill within the scope of the present disclosure as well.

The chassis 302 also includes a subscriber optical network connector 310(e.g., a duplex optical connector) that is configured to couple to anoptical connector on an optical cable, and the subscriber IC-TROSAdevice 308 is coupled to the subscriber optical network connector 310via an optical transmit connection 310 a and an optical receiveconnection 310 b. The chassis 302 also includes one or more subscriberITLA device(s) 312 that are coupled to the subscriber IC-TROSA device308. Similarly as described above for the hub ITLA device 214, thesubscriber ITLA device(s) 312 may be configured to providehighly-coherent, narrow-linewidth laser light waves described by complexelectrical fields referred to as a receiver local oscillator electricalfield E_(L) and a transmitter laser source electrical field E_(St), andone of skill in the art in possession of the present disclosure willrecognize that the receiver local oscillator electrical field E_(L) andthe transmitter laser source electrical field E_(St) may be provided atthe same wavelength or different wavelengths.

Furthermore, one of skill in the art in possession of the presentdisclosure will appreciate that a single subscriber ITLA device mayprovide both the receiver local oscillator electrical field E_(L) andthe transmitter laser source electrical field E_(St) or separatesubscriber ITLA devices may provide the receiver local oscillatorelectrical field E_(L) and the transmitter laser source electrical fieldR_(St), while remaining within the scope of the present disclosure.Further still, while illustrated as a separate device, one of skill inthe art in possession of the present disclosure will recognize that thesubscriber ITLA device(s) 312 may be integrated into the subscriberIC-TROSA device 308 while remaining within the scope of the presentdisclosure as well. However, while a specific subscriber coherentoptical transceiver device 300 has been illustrated and described, oneof skill in the art in possession of the present disclosure willrecognize that subscriber coherent optical transceiver device devices(or other devices operating according to the teachings of the presentdisclosure in a manner similar to that described below for thesubscriber coherent optical transceiver device 300) may include avariety of components and/or component configurations for providingconventional subscriber coherent optical transceiver devicefunctionality, as well as the functionality discussed below, whileremaining within the scope of the present disclosure as well.

Referring now to FIG. 4 , an embodiment of a hub IC-TROSA device 400 isillustrated that may provide the hub IC-TROSA device 208 discussed abovewith reference to FIG. 2 . As will be appreciated by one of skill in theart in possession of the present disclosure, the hub IC-TROSA device 400may be based on photonic integrated circuits (PICs) that include opticalwaveguides at or near the surface of a planar substrate that utilizessubstrate materials such as silicon (Si - also known as siliconphotonics), indium phosphide (InP), silica (SiO₂) and lithium niobate(LiNbO₃), and/or other substrate materials known in the art. While it isoften advantageous for both transmit subsystems and receive subsystems(discussed below) in an IC-TROSA device to be fabricated on the samesubstrate, both conventional IC-TROSA devices and the hub IC-TROSAdevice of the present disclosure may utilize transmit subsystems andreceive subsystems fabricated on distinct substrates that may be basedon different materials, and alternate embodiments of the hub IC-TROSAdevice 400 discussed below may utilize discrete optical components or ahybrid-mix of discrete and integrated optical components.

In the illustrated embodiment, the hub IC-TROSA device 400 includes achassis 402 that houses the components of the hub IC-TROSA device 400,only some of which are illustrated and described below. As will beappreciated by one of skill in the art in possession of the presentdisclosure, the illustrated embodiment of the hub IC-TROSA device 400provides schematic details of a hub IC-TROSA transmit subsystem and ahub IC-TROSA receive subsystem that are provided according to theteachings of the present disclosure, and omits many components that oneof skill in the art will recognize would be included in an IC-TROSAdevice for clarity of discussion. For example, while not illustrated,the hub IC-TROSA device of the present disclosure may include adjustable(thermal and/or electro-optic) phase controllers, optical phase delays,adjustable modulator bias control, optical taps, photo-detectors,monitor photodiodes, beam splitters, traces for electrical signals,local heaters, temperature sensors, optical amplifiers, variable opticalattenuators, polarization rotators/controllers and polarization beamcombiners/splitters, as well as other IC-TROSA components that would beapparent to one of skill in the art in possession of the presentdisclosure. As will be appreciated by one of skill in the art inpossession of the present disclosure, optimized implementations of thehub IC-TROSA device of the present disclosure may include theappropriate use of one or more of components discussed above (e.g., biasvoltage control of the optical directional couplers discussed in furtherdetail below, as well as monitor photodiodes, may be useful in suchoptimization).

The hub IC-TROSA transmit subsystem in the embodiment illustrated inFIG. 4 may be provided by a quadrature optical modulator subsystem 404that includes an optical input 404 a that may be coupled to the hub ITLAdevice 214, and that may be configured to receive light that includesthe transmitter laser source electrical field E_(St) provided by the hubITLA device 214. As will be appreciated by one of skill in the art inpossession of the present disclosure, the quadrature optical modulatorsubsystem in the hub IC-TROSA device 400 may (and typically will)include a pair of quadrature optical modulator devices (e.g., a Iquadrature optical modulator device and an Q quadrature opticalmodulator device) that operate to double the data capacity of the hubIC-TROSA transmit subsystem, and each quadrature optical modulatordevice may be configured similarly to the quadrature optical modulatorsubsystem 404 described herein. Furthermore, while the discussion hereinis related to coherent optical signal transmission via a singlepolarization, one of skill in the art in possession of the presentdisclosure will appreciate how the use of dual polarization within thehub IC-TROSA transmit subsystem via two quadrature optical modulatordevices (e.g., with the quadrature optical modulator devices modulatingdata into orthogonal polarizations of a light wave, and with thedistinct polarizations combined with polarization beam combiners) willprovide substantial benefits as well.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, the quadrature optical modulator subsystem 404 alsoincludes a pair of Mach-Zehnder (MZ) interferometer devices 404 b and404 c. In the illustrated embodiment, the MZ interferometer device 404 bis coupled to the optical input 404 a and includes a +φ_(l)(t) phasemodulator 404 d directly coupled to the optical input 404 a, and a-φ_(l)(t) phase modulator 404 e coupled to the optical input 404 a by aπ phase shifter 404 f, with the +φ_(l)(t) phase modulator 404 dincluding a connection 404 g to the hub signal processing engine 204(e.g., via a modulator driver, not illustrated in FIGS. 2 and 4 ), andthe -φ_(l)(t) phase modulator 404 e including a connection 404 h to thehub signal processing engine 204 (e.g., via a modulator driver, notillustrated in FIGS. 2 and 4 ). The MZ interferometer device 404 c iscoupled to the optical input 404 a and includes a +φ_(Q)(t) phasemodulator 404 i directly coupled to the optical input 404 a, and a-φ_(Q)(t) phase modulator 404 j coupled to the optical input 404 a by aπ phase shifter 404 k, with the +φ_(Q)(t) phase modulator 404 iincluding a connection 4041 to the hub signal processing engine 204(e.g., via a driver, not illustrated in FIGS. 2 and 4 ), and the-φ_(Q)(t) phase modulator 404 j including a connection 404 m to the hubsignal processing engine 204 (e.g., via a modulator driver, notillustrated in FIGS. 2 and 4 ).

As will be appreciated by one of skill in the art in possession of thepresent disclosure, each path to the MZ interferometer devices 404 b and404 c may be driven in a “push/pull” fashion by voltages to generate adifferential optical phase shift of +φ_(lQ)(t) (i.e., via theelectro-optic effect). Furthermore, one of skill in the art inpossession of the present disclosure will appreciate that each of the MZinterferometer devices 404 b and 404 c may be driven by a four-levelPulse Amplitude Modulation (4-PAM) signal, and the output of theinterferometer devices 404 b and 404 c may be provided via the16-Quadrature Amplitude Modulation (16-QAM) optical signal modulationformat that describes a 4-bit/16 element symbol or constellation.

While the present disclosure describes the quadrature optical modulatorsubsystem 404 utilizing MZ interferometer devices 404 b and 404 c, oneof skill in the art will appreciate how the quadrature optical modulatorsubsystem may instead utilize optical ring resonators [e.g., see P.Dong, C. Xie, L. L. Buhl and Y. Chen, “Silicon Microring Modulators forAdvanced Modulation Formats,” presented at Optical Fiber CommunicationConference (OFC), Anaheim, USA, 2013, paper OW4J.2], electro-absorptionmodulators [e.g., see I. Kang, “Phase-shift-keying and on-off-keyingwith improved performances using electroabsorption modulators withinterferometric effects,” Optics Express, vol. 15, no. 4, pp. 1467-1473,2007], directly modulated lasers [e.g., see P. Dong, A. Melikyan, K.Kim, N.Kaneda, B. Stern and Y. Baeyens, “In-phase/quadrature modulationusing directly reflectivity-modulated laser,” Optica, vol. 7, no.8 pp.929-933, 2020], and/or other techniques for providing the functionalitydescribed below.

The quadrature optical modulator subsystem 404 also includes an opticaldirectional coupler device 404 n that receives a respective outputs fromeach of the MZ interferometer devices 404 b and 404 c as inputs, andprovides respective outputs via a first optical transmit connection 406a (which may provide the first optical transmit connection 210 adiscussed above with reference to FIG. 2 ), and a second opticaltransmit connection 406 b (which may provide the second optical transmitconnection 212 a). One of skill in the art in possession of the presentdisclosure will recognize that the optical directional coupler device404 n may be relatively sensitive to optical wavelength, and thus may beadjusted for different wavelengths of light provided by ITLA device(s)(e.g., via optical sensors coupled to the first optical transmitconnection 406 a and/or the second optical transmit connection 406 b inorder to accommodate optimization of the optical directional couplerdevice 404 n via a closed-loop feedback system). As will be appreciatedby one of skill in the art in possession of the present disclosure, thefirst optical transmit connection 406 a may be configured to transmitoptical signals having an I quadrature and a Q quadrature that differ inoptical phase by +π/2 radians, while the second optical transmitconnection 406 b may be configured to transmit optical signals havingthe I quadrature and the Q quadrature that differ in optical phase by -π/2 radians, with the light waves providing the optical signals to boththe first optical transmit connection 406 a and the second opticaltransmit connection 406 b having identical average power and carryingidentical information with information components (i.e., quadratures) ina different optical phase relationship.

In another embodiment, the optical directional coupler device 404 ndiscussed above may be replaced by optical amplifier devices (e.g.,integrated into the hub IC-TROSA device 400 or the hub coherent opticaltransceiver device 200, coupled to the hub coherent optical transceiverdevice 200, etc.) that support the dual transmit connections 406 a and406 b (i.e., at the expense of higher power consumption, increased heatdissipation requirements, and additional space requirements) and thatare located between a single-output 2×1 Y-junction and a dual-output 1×2Y junction. For example, such optical amplifier devices may operate toamplify the output power of optical signals produced by the quadratureoptical modulator subsystem 404 to produce amplified output signals(e.g., with double the output power of the optical signals produced bythe quadrature optical modulator subsystem 404), and provide thoseamplified optical signals to a 1×2 Y-junction optical waveguide thatprovides the dual transmit connections 406 a and 406 b that each outputoptical signals with output power equivalent to the output power of theoptical signals produced by the quadrature optical modulator subsystem404. As will be appreciated by one of skill in the art in possession ofthe present disclosure, the use of such optical amplifiers as discussedabove adds costs and requires additional power for the opticalamplification, and the resulting optical signals may be degraded (e.g.,by the finite noise figure of the optical amplifiers).

As illustrated, the hub IC-TROSA receive subsystem in the embodimentillustrated in FIG. 4 may also include an optical hybrid mixer subsystem408, which one of skill in the art in possession of the presentdisclosure will recognize may be provided by a 90-degree hybrid opticalmixer device and/or other optical hybrid mixer subsystems known in theart. As will be appreciated by one of skill in the art in possession ofthe present disclosure, the hub IC-TROSA device 400 may (and typicallywill) include a pair of optical hybrid mixer devices (e.g., aX-polarization 90-degree hybrid mixer device and a Y-polarization90-degree hybrid mixer device) that operate to double the data capacityof the hub IC-TROSA receive subsystem, and that each optical hybridmixer device may be configured similarly to the optical hybrid mixersubsystem 408 described herein. Furthermore, while the discussion hereinis related to coherent optical signal reception via a singlepolarization, one of skill in the art in possession of the presentdisclosure will appreciate how the use of dual polarization with the hubIC-TROSA receive subsystem via two optical hybrid mixer devices (e.g.,with the optical hybrid mixer devices receiving data that was modulatedinto orthogonal polarizations of a light wave, and using a polarizationbeam splitter to separate the received light wave into orthogonalpolarization states, and with signal processing operations utilized torecover the data from those orthogonal polarization states) will providesubstantial benefits as well. In the illustrated embodiment, the opticalhybrid mixer subsystem 408 includes an optical directional couplerdevice 408 a having a first optical receive connection 410 a (which maybe provided by the first optical receive connection 210 b discussedabove with reference to FIG. 2 ), and a second optical receiveconnection 410 b (which may be provided by the second optical receiveconnection 212 b).

In the illustrated embodiment, the optical hybrid mixer subsystem 408includes an optical directional coupler device 408 b that is configuredto receive light having the receiver local oscillator electrical fieldE_(L) provided by the hub ITLA device 214 at one of its inputs, with theother input of the optical directional coupler device 408 b unused, andone of skill in the art in possession of the present disclosure willrecognize how the optical directional coupler device 408 b may bereplaced by a 1×2 Y-junction optical waveguide that is configured toreceive light having the receiver local oscillator electrical fieldE_(L) from the hub ITLA device 214 while remaining within the scope ofthe present disclosure as well.

As can be seen in FIG. 4 , the optical directional coupler device 408 ais configured to mix the optical signals received via the first opticalreceive connection 410 a and the second optical receive connection 410 bto generate a “first mixed signal” and a “second mixed signal”, andprovide the first mixed signal through a π/2 phase shifter 408 c in theoptical hybrid mixer subsystem 408. Furthermore, an optical directionalcoupler device 408 d is coupled to the π/2 phase shifter 408 c and theoptical directional coupler device 408 b in the optical hybrid mixersubsystem 408, and is configured to mix the first mixed signal receivedvia the π/2 phase shifter 408 c and the light with the receiver localoscillator electrical field E_(L) to generate a “third mixed signal” anda “fourth mixed signal”, and provide the third mixed signal through aphoto diode (PD) 408 e, a transimpedance amplifier (TIA) 408 f, and to afirst input on a differential amplifier 408 g, while providing thefourth mixed signal through a PD 408 h, a TIA 408 i, and to a secondinput on the differential amplifier 408 g.

Further still, an optical directional coupler device 408 j is coupled tothe optical directional coupler devices 408 a and 408 b in the opticalhybrid mixer subsystem 408, and is configured to mix the second mixedsignal and light having the receiver local oscillator electrical fieldE_(L) to generate a “fifth mixed signal” and a “sixth mixed signal”, andprovide the fifth mixed signal through a PD 408 k, a TIA 408 l, and to afirst input on a differential amplifier 408 m, while providing the sixthmixed signal through a PD 408 n, a TIA 408 o, and to a second input onthe differential amplifier 408 m. As will be appreciated by one of skillin the art in possession of the present disclosure, the hub IC-TROSAreceive subsystem illustrated in FIG. 4 is configured to convert theoptical signals received at the first optical receive connection 410 aand the second optical receive connection 410 b to electrical signals(i.e., voltages) at outputs 408 p and 408 q of the differentialamplifiers 408 g and 408 m, respectively, discussed in further detailbelow. As will be appreciated by one of skill in the art in possessionof the present disclosure, while illustrated and described as internalto the hub IC-TROSA device 400, the PDs, TIAs, and/or differentialamplifiers may be external to the hub IC-TROSA device 400, may beintegrated in the hub signal processing engine 204, and/or may beprovided in other manners while remaining within the scope of thepresent disclosure as well.

As such, while a specific hub IC-TROSA device 400 has been illustratedand described, one of skill in the art in possession of the presentdisclosure will appreciate how hub IC-TROSA devices provided accordingto the teachings of the present disclosure may include other componentsand/or component configurations for providing the functionalitydiscussed below while remaining within the scope of the presentdisclosure as well. For example, while the embodiments of the hubIC-TROSA device 400 illustrated and described herein include both thehub IC-TROSA transmit subsystem with dual transmit connections 406 a and406 b, along with the hub IC-TROSA transmit subsystem with dual receiveconnections 410 a and 410 b, other embodiments may provide either thehub IC-TROSA transmit subsystem with dual transmit connections 406 a and406 b, or the hub IC-TROSA transmit subsystem with dual receiveconnections 410 a and 410 b, while remaining within the scope of thepresent disclosure as well.

For example, FIG. 5 illustrates another embodiment of a hub IC-TROSAdevice 500 that may provide the hub IC-TROSA device 208 discussed abovewith reference to FIG. 2 , and that includes some components that arethe same as the IC-TROSA device 400 discussed above with reference toFIG. 4 , with common components provided with the same element numbers.As such, the hub IC-TROSA device 500 includes the chassis 402 thathouses the hub IC-TROSA transmit subsystem provided by the quadratureoptical modulator subsystem 404 described above. However, the hubIC-TROSA receive subsystem in the embodiment illustrated in FIG. 5 mayinclude an optical hybrid mixer subsystem 502, which one of skill in theart in possession of the present disclosure will recognize may beprovided by a multimode interference (MMI) device that includes amultimode waveguide 502 a coupled to a plurality of single-modewaveguides 502 b, 502 c, 502 d, 502 e, 502 f, 502 g, and 502 h. As willbe appreciated by one of skill in the art in possession of the presentdisclosure, the optical hybrid mixer subsystem in the hub IC-TROSAdevice 500 may (and typically will) include a pair of MMI devices (e.g.,one for each polarization), and that each MMI device may be configuredsimilarly to the optical hybrid mixer subsystem 502 described herein. Inthe examples discussed below, the optical hybrid mixer subsystem 502 mayinclude optical phase relationships between its input ports and outputports that are described by the table below:

OUTPUT 1 2 3 4 INPUT 1 0 3π/4 -π/4 0 2 3π/4 0 0 -π/4 3 -π/4 0 0 3π/4 4 0-π/4 3π/4 0

In the illustrated embodiment, the single-mode waveguide 502 b on theoptical hybrid mixer subsystem 502 is configured to receive light havingthe receiver local oscillator electrical field E_(L) from the hub ITLAdevice 214, the single-mode waveguide 502 c on the optical hybrid mixersubsystem 502 is coupled to a first optical receive connection 504 a(which may be provided by the first optical receive connection 210 bdiscussed above with reference to FIG. 2 ), and the single-modewaveguide 502 d is coupled to a second optical receive connection 502 d(which may be provided by the second optical receive connection 212 b).Furthermore, the single-mode waveguide 502 e on the optical hybrid mixersubsystem 502 is coupled to a PD 502 i, a TIA 502 j, and to a firstinput on a differential amplifier 502 k; the single-mode waveguide 502 fon the optical hybrid mixer subsystem 502 is coupled to a PD 502 l, aTIA 502 m, and to a first input on a differential amplifier 502 n; thesingle-mode waveguide 502 g on the optical hybrid mixer subsystem 502 iscoupled to a PD 502 o, a TIA 502 p, and to a second input on thedifferential amplifier 502 n; and the single-mode waveguide 502 h on theoptical hybrid mixer subsystem 502 is coupled to a PD 502 q, a TIA 502r, and to a second input on the differential amplifier 502 k. As will beappreciated by one of skill in the art in possession of the presentdisclosure, the hub IC-TROSA receive subsystem illustrated in FIG. 5 isconfigured to convert the optical signals received at the first opticalreceive connection 504 a and the second optical receive connection 504 bto electrical signals (i.e., voltages) at outputs 502s and 502 t of thedifferential amplifiers 502 k and 502 n, respectively, discussed infurther detail below.

With reference to FIGS. 6 and 7 , the hub coherent optical transceiverdevice 200 may be provided on a hub device 600. In an embodiment, thehub device 600 may be provided by the IHS 100 discussed above withreference to FIG. 1 and/or may include some or all of the components ofthe IHS 100, and in specific examples may be provided by a networkingdevice (e.g., a switch device, a router device, a subscriber gatewaydevice, a radio unit device, etc.) and/or other computing devices thatwould be apparent to one of skill in the art in possession of thepresent disclosure. As discussed above, in many embodiments the hubcoherent optical transceiver device 200 may be provided as a pluggablemodule that may be connected to a port on the hub device 600 (e.g., ahost provided by the hub device 600), as illustrated in FIG. 7 ,although embodiments in which the hub coherent optical transceiverdevice 200 is integrated in the hub device 600 will fall within thescope of the present disclosure as well. FIG. 6 also illustrates how arespective one of the subscriber coherent optical transceiver devices300 may be provided on each of a plurality of subscriber devices 602 aand 602 b. In an embodiment, any or all of the subscriber devices 602 aand 602 b may be provided by the IHS 100 discussed above with referenceto FIG. 1 and/or may include some or all of the components of the IHS100, and in specific examples may be provided by server devices,networking devices (e.g., switch devices or router devices), subscribergateway devices, storage systems, and/or other computing devices thatwould be apparent to one of skill in the art in possession of thepresent disclosure. As discussed above, in many embodiments thesubscriber coherent optical transceiver devices 300 may be provided aspluggable modules that may be connected to a port on the subscriberdevices 602 a and 602 b, although embodiments in which the subscribercoherent optical transceiver devices 300 are integrated in thesubscriber devices 602 a and 602 b will fall within the scope of thepresent disclosure as well.

FIG. 6 illustrates how the connector 210 on the hub coherent opticaltransceiver device 200 that is coupled to the first optical transmitconnection 210 a and first optical receive connection 210 b is connectedto the respective subscriber coherent optical transceiver devices 300provided with each the subscriber devices 602 a by a Passive OpticalNetwork (PON) 604 that, as described in further detail below, provides afirst point-to-multipoint optical network. FIG. 6 also illustrates howthe connector 212 on the hub coherent optical transceiver device 200that is coupled to the second optical transmit connection 212 a andsecond optical receive connection 212 b is connected to the respectivesubscriber coherent optical transceiver devices 300 provided with eachthe subscriber devices 602 b by a PON 606 that, as described in furtherdetail below, provides a second point-to-multipoint optical network. Oneof skill in the art will recognize that the coupling of the hub device600 and subscriber devices 602 a in FIG. 6 has been greatly simplified,and in actual implementation may include asymmetric Y-couplers ofdifferent asymmetries, and/or other components that would be apparent toone of skill in the art. Furthermore, as will be appreciated by one ofskill in the art in possession of the present disclosure, the PONs 604and 606 may be provided as a connection to a 1xN optical splitter,although other PON provisioning techniques are envisioned as fallingwithin the scope of the present disclosure as well.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, the PONs 604 and 606 are illustrated and describedbelow as provided by bi-directional optical networks and, as such, thePONs 604 and 606, the hub coherent optical transceiver device 200,and/or the subscriber coherent optical transceiver devices 300 mayinclude optical circulators that are configured to, for example, combinelight waves traveling in opposite directions into a single optical fiberin order to decrease the overall fiber count in that optical network.However, one of skill in the art in possession of the present disclosurewill appreciate that each of the bi-direction optical networksillustrated herein may be replaced with a respective pair of parallelpoint-to-multipoint optical networks that include a first/upstreamoptical network and a second/downstream optical network while remainingwithin the scope of the present disclosure as well.

Referring now to FIG. 8 , an embodiment of a conventional IC-TROSAdevice 800 is illustrated and described briefly for purposes ofidentifying issues with its operation, as well as to contrast thebenefits of the teachings of the present disclosure. As illustrated, theconventional IC-TROSA device 800 includes a chassis 802 that houses anIC-TROSA transmit subsystem 804 and an IC-TROSA receive subsystem 806.As will be appreciated by one of skill in the art in possession of thepresent disclosure, the IC-TROSA transmit subsystem 804 in theconventional IC-TROSA device 800 includes a quadrature optical modulatordevice having a single 2×1 single-mode Y-junction 804 a that provides asingle optical transmit connection 804 b, while the IC-TROSA receivesubsystem 806 in the conventional IC-TROSA device 800 includes a90-degree optical hybrid mixer device having a 1×2 single-modeY-junction 806 a that provides a single optical receive connection 806b. As will be appreciated by one of skill in the art in possession ofthe present disclosure, the conventional IC-TROSA device 800 may beprovided in conventional coherent optical transceiver devices, and thusthe discussions of the use and/or operation of the conventional IC-TROSAdevice 800 below may assume the presence of the conventional coherentoptical transceiver device while omitted its illustration and discussionfor clarity.

Referring now to FIG. 9 , an embodiment of the coupling of theconventional IC-TROSA device 800 (e.g., a hub IC-TROSA device in a hubcoherent optical transceiver device) to subscriber devices 900 via apoint-to-multipoint optical network 902 is illustrated and describedbriefly for purposes of identifying issues with its operation, as wellas to contrast the benefits of the teachings of the present disclosure.One of skill in the art in possession of the present disclosure willrecognize that the point-to-multipoint optical network 902 may be abi-directional optical network that may include the optical circulatorsor a pair of parallel point-to-multipoint optical networks similarly asdiscussed above. As illustrated, the optical transmit connection 804 band the optical receive connection 806 b on the conventional IC-TROSAdevice 800 may couple to a port on a conventional hub coherent opticaltransceiver device (not illustrated), and the point-to-multipointoptical network 902 may be connected to that port as well as to each ofthe subscriber devices 900. FIG. 9 illustrates how thepoint-to-multipoint optical network 902 may include a plurality of 1×2single-mode Y-junction optical waveguides 902 a, 902 b, 902 c, 902 d,902 e, 902 f, 902 g, 902 h, 902 i, 902 j, 902 k, 902 l, 902 m, 902 n,and 902 o (i.e., in theconventional-hub-IC-TROSA-device-to-subscriber-device direction) inorder to split the connection from the conventional IC-TROSA device 800to 16 subscriber devices 900. As will be appreciated by one of skill inthe art in possession of the present disclosure, while the 1×2single-mode Y-junction optical waveguides 902 a-902 o are illustratedseparately, those 1×2 single-mode Y-junction optical waveguides 902a-902 o may be provided by a single 1xN splitter device while remainingwithin the scope of the present disclosure.

With reference to FIG. 10 , an embodiment of the operation of a 2×1single-mode Y-junction optical waveguide 1000 with optical inputs 1002 aand 1002 b and optical output 1004 is illustrated to briefly discussissues with those devices. The 2×1 single-mode Y-junction opticalwaveguide 1000 may be fabricated on a planar optical substrate (e.g., aPlanar Lightwave Circuit (PLC) or Photonic Integrated Circuit (PIC)),and may be aggregated with other single-mode Y-junctions to form a 1×Nsingle-mode optical splitter and may be fabricated with materials thatwould be apparent to one of skill in the art in possession of thepresent disclosure. As will be appreciated by one of skill in the art inpossession of the present disclosure, the calculations below based onthe optical component diagrams and/or discussions below (with referenceto FIG. 10 as well as any of the other calculations provided herein)assume that the corresponding optical components are loss-less (exceptfor the “waste light” discussed below), but actual physical devices willinclude some optical loss that, when included in the calculationsdiscussed below, would change results slightly (without changing thefundamental teachings of the present disclosure).

In the illustrated embodiment, the 2×1 single-mode Y-junction opticalwaveguide 1000 includes the first input 1002 a that is configured toreceive signals provided by a highly-coherent, narrow-linewidth laserlight wave that are described by a complex electrical field E₁ (referredto below as “E₁ lightwave”), the second input 1002 a that does notreceive signals, and the output 1004. As illustrated, when the E₁lightwave traverses the 2×1 single-mode Y-junction optical waveguide1000 from the first input 1002 a, the portion of the E₁lightwave that isdirected via the output 1004 of the 2×1 single-mode Y-junction opticalwaveguide 1000 may be described by a complex electrical field, E₁/√2representing a reduction in the light power of the lightwave traversingthe 2×1 single-mode Y-junction optical waveguide 1000 by half, with the“missing” light power radiating from the 2×1 single-mode Y-junctionoptical waveguide 1000 as “waste light” 1006 (a result that one of skillin the art in possession of the present disclosure will recognize can beproven via the application of Maxwell’s equations, or by invoking thesecond law of thermodynamics).

With reference to FIG. 11 and the conventional IC-TROSA device 800discussed above with reference to FIG. 8 , the transmission of signalsvia the IC-TROSA transmit subsystem 804 and through the 2×1 single-modeY-junction optical waveguide 804 a will thus include waste light 1100,providing the corresponding reduction in the light power of signalstransmitted from the IC-TROSA transmit subsystem 804 and out of theoptical transmit connection 804 b by approximately half due to thelosses provided by the 2×1 single-mode Y-junction optical waveguide 804a. As will be appreciated by one of skill in the art in possession ofthe present disclosure, the hub IC-TROSA device 400 replaces the 2×1single-mode Y-junction optical waveguide 804 a with the opticaldirectional coupler device 404 n, thus doubling the number of equivalentoptical transmit connections relative to the conventional IC-TROSAdevice 800 while eliminating the waste light 1100, as discussed infurther detail below.

Similarly, with reference to FIG. 12 and the coupling of theconventional IC-TROSA device 800 to subscriber devices 900 via apoint-to-multipoint optical network 902 discussed above with referenceto FIG. 9 , the transmission of signals from any of the subscriberdevices 900 to the conventional IC-TROSA device 800 and through anysubset of the 2×1 single-mode Y-junction optical waveguides 902 a-902 o(i.e., in the subscriber-device-to-conventional-IC-TROSA-devicedirection) will thus include corresponding waste light 1200 at thatsubset of 2x1 single-mode Y-junction optical waveguides, providing thecorresponding reduction in the light power of signals transmitted fromthat subscriber device and through those 2×1 single-mode Y-junctionoptical waveguides by approximately half at each of those 2×1single-mode Y-junction optical waveguides due to the losses provided bythose 2×1 single-mode Y-junction optical waveguides. As will beappreciated by one of skill in the art in possession of the presentdisclosure, the hub IC-TROSA device 400 replaces the 2×1 single-modeY-junction optical waveguide 902 a with the optical directional couplerdevice 408 a, thus doubling the number of optical receive connectionsrelative to the conventional IC-TROSA device 800 while eliminating thewaste light 1200 from the 2×1 single-mode Y-junction optical waveguide902 a (while connecting the 2×1 single-mode Y-junction opticalwaveguides 902 b and 902 c to respective ones of those optical receiveconnections.

Referring now to FIG. 13 , an embodiment of a method 1300 fortransmitting data from a hub device to a subscriber device via apoint-to-multipoint optical network is illustrated. As discussed below,the systems and methods of the present disclosure include a hub IC-TROSAdevice with an optical directional coupler device that substantiallyeliminates optical signal loss produced by conventional hub IC-TROSAdevices while providing dual optical transmit connections that allow thehub IC-TROSA device to transmit two optical signals (via the respectivetransmit connections) to different point-to-multipoint optical networks.For example, the hub IC-TROSA point-to-multipoint optical network systemof the present disclosure may include a point-to-multipoint opticalnetwork that is coupled to subscriber devices, and that is coupled to ahub device via a hub IC-TROSA device included in a hub coherent opticaltransceiver device coupled to the hub device. The hub IC-TROSA deviceincludes a quadrature optical modulator subsystem, and an opticaldirectional coupler device in the quadrature optical modulator subsystemprovides a first transmit connection and a second transmit connection tothe point-to-multipoint optical network. The optical directional couplerdevice receives first optical signals from the quadrature opticalmodulator subsystem and transmits them via the first transmit connectionto a first subset of the subscriber devices via the point-to-multipointoptical network, and receives second optical signals from the quadratureoptical modulator subsystem and transmits them via the second transmitconnection to a second subset of the subscriber devices via thepoint-to-multipoint optical network. As discussed below, the hubIC-TROSA device of the present disclosure increases the distance opticalsignals may be transmitted, or increases the number of subscriberdevices to which optical signals may be transmitted over a particulardistance, via point-to-multipoint networks relative to conventional hubIC-TROSA devices.

The method 1300 begins at block 1302 where a hub coherent opticaltransceiver device generates first optical signals and second opticalsignals. With reference to FIGS. 6, 14A, and 14B, in an embodiment ofblock 1302, the hub device 600 may provide data (e.g., via electricalsignals) to the hub coherent optical transceiver device 200 via the hubdevice connector 206, and the hub device connector 206 may perform datatransmission operations 1400 that may include transmitting the data(e.g., via electrical signals) through the data input connection 204 aand to the hub signal processing engine 204. Furthermore, the hub ITLAdevice 214 may perform light provisioning operations 1402 by generatingand transmitting light (e.g., via a laser) to the hub IC-TROSA device208 such that light having the transmitter laser source electrical fieldE_(St) is received at the optical input 404 a. The hub signal processingengine 204 may then utilize the data received via the data inputconnection 204 a from the hub device connector 206 to perform signalgeneration operations 1404 that include transmitting signal generationcommands (based on the data) via the connections 404 g and 404 h to the+φ_(l)(t) phase modulator 404 d and the -φ_(l)(t) phase modulator 404 e,respectively, in the MZ interferometer device 404 b of the quadratureoptical modulator subsystem 404 (e.g., to instruct the generation ofoptical signals), and transmitting signal generation commands (based onthe data) via the connections 4041 and 404 m to the +φ_(Q)(t) phasemodulator 404 i and the -φ_(Q)(t) phase modulator 404 j, respectively,in the MZ interferometer device 404 b and 404 c of the quadratureoptical modulator subsystem 404 (e.g., to instruct the generation ofoptical signals).

As illustrated in FIG. 14B, the π phase shifters 404 f and 404 k, the+φl (t) phase modulator 404 d, the -φ_(l)(t) phase modulator 404 e, the+φ_(Q)(t) phase modulator 404 i, and the -φ_(Q)(t) phase modulator 404 joperate (using the light having the transmitter laser source electricalfield E_(St) along with the signal generation commands transmitted bythe hub signal processing engine 204) to provide respective opticalsignals to the optical directional coupler device 404 n, and the opticaldirectional coupler device 404 n operates to mix those respectiveoptical signals to produce first optical signals at the first opticaltransmit connection 406 a described by the following equation:

E_(St)(sin [φ_(I)(t)] + isin [φ_(Q)(t)])/2

One of skill in the art in possession of the present disclosure willappreciate that the first optical signals described by the equationabove include a I quadrature and a Q quadrature have a first phaserelationship that differs in optical phase by +π/2 radians.

Furthermore, the π phase shifters 404 f and 404 k, the +φ_(l)(t) phasemodulator 404 d, the -φ_(l)(t) phase modulator 404 e, the +φ_(Q)(t)phase modulator 404 i, and the -φ_(Q)(t) phase modulator 404 j operate(using the light having the transmitter laser source electrical fieldE_(St)along with the signal generation commands transmitted by the hubsignal processing engine 204) to provide respective optical signals tothe optical directional coupler device 404 n, and the opticaldirectional coupler device 404 n operates to mix those respectiveoptical signals to produce second optical signals at the second opticaltransmit connection 406 b described by the following equation:

iE_(St)(sin [φ_(I)(t)] − isin [φ_(Q)(t)])/2

One of skill in the art in possession of the present disclosure willappreciate that the second optical signals described by the equationabove include the I quadrature and the Q quadrature have a second phaserelationship that differs in optical phase by -π/2 radians.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, because both lightwaves E₁ and E₂ describing thefirst and second optical signals have the same (angular) optical carrierfrequency ω₀, |E₁(ω₀ + ω)|² = |E₂{w₀ - ω) |². In other words, theoptical power spectral density of the first and second lightwaves aremirror images of each other about ω₀ in optical frequency space. Assuch, one of skill in the art in possession of the present disclosurewill recognize how, in the case of a coherent PON with digital opticalsubcarriers, subscriber transceivers will detect information-bearingoptical subcarriers at different and distinct optical frequenciesdepending on whether they receive the first or second optical signals

With reference to FIG. 15 , the generation of optical signals by theconventional hub IC-TROSA device 800 discussed above with reference toFIG. 8 is illustrated. As can be seen, when light having a transmitterlaser source electrical field E_(St) is provided to the IC-TROSAtransmit subsystem 804 in the conventional hub IC-TROSA device 800, theoutput of the 2×1 single-mode Y-junction optical waveguide 804 a at theoptical transmit connection 804 b will be an optical signal described bythe following equation:

E_(St)(sin [φ_(I)(t)] + isin [φ_(Q)(t)])/2

As such, with reference back to FIG. 14B, one of skill in the art inpossession of the present disclosure will appreciate how the firstoptical signals produced at the first optical transmit connection 406 aby the quadrature optical modulator subsystem 404 may be the same asthose produced at the optical transmit connection 804 b by the IC-TROSAtransmit subsystem 804 in the conventional hub IC-TROSA device 800.

With reference to FIG. 16 , an embodiment of an optical directionalcoupler device 1600 is illustrated that may provide the opticaldirectional coupler device 404 n in the quadrature optical modulatorsubsystem 404, and that includes a first input 1602 a, a second input1602 b, a first output 1604 a, and a second output 1604 b. In theembodiments discussed herein, optical directional coupler devices areprovided with the following transfer function:

$\begin{bmatrix}E_{1}^{\text{out}} \\E_{2}^{\text{out}}\end{bmatrix} = \frac{1}{\sqrt{2}}\begin{bmatrix}1 & i \\i & 1\end{bmatrix}\begin{bmatrix}E_{1}^{in} \\E_{2}^{in}\end{bmatrix}$

One of skill in the art in possession of the present disclosure willappreciate that the transfer function above is a design choice, and ageneric transfer function may be provided by:

$\begin{bmatrix}E_{1}^{\text{out}} \\E_{2}^{\text{out}}\end{bmatrix} = \begin{bmatrix}{\cos\theta} & {e^{i\phi}\sin\theta} \\{- e^{- i\phi}\sin\theta} & {\cos\theta}\end{bmatrix}\begin{bmatrix}E_{1}^{in} \\E_{2}^{in}\end{bmatrix}$

where θ and are Φ are (real) design parameters.

In some embodiments, the transfer function of the optical directionalcoupler device may be adjusted or controlled by applying a bias voltageor voltages to appropriate electrodes in the vicinity of the opticalwaveguides that make up the optical directional coupler device. Asdiscussed above, the transfer function of the optical directionalcoupler device may be sensitive to the wavelength of the lightwaveE_(St) originating at hub ITLA 204. Thus, in some examples, one or moreof the optical directional couplers devices described herein may includeelectrodes that allows its transfer function to be adjusted for optimalperformance by application or a bias voltage or voltages. For example,as discussed above, optical taps, photodetectors, and/or other devicesmay be incorporated into the IC-TROSA device 500 or 600 to facilitateclosed loop control of the bias applied to directional coupler 404 n foroptimum IC-TROSA performance. Furthermore, other embodiments of thepresent disclosure may utilize alternate designs, which one of skill inthe art in possession of the present disclosure will appreciate willinfluence the calculation of the quadrature optical modulator subsystemtransfer functions and optical hybrid mixer subsystem transferfunctions.

As can be seen in FIG. 16 , when the first input 1602 a of the opticaldirectional coupler device 1600 is provided light having an electricalfield E₁ and the second input 1602 b of the optical directional couplerdevice 1600 is provided light having an electrical field E₂, the lightprovided at the first output 1604 a of the optical directional couplerdevice 1600 will have an electrical field (E₁ + iE₂)_(/)√2, and thelight provided at the second output 1604 b of the optical directionalcoupler device 1600 will have an electrical field (iE₁ + E₂)/√2 if, forexample, the directional optical coupler device 1600 is configured tooperate with the transfer function of the equation referenced above. Assuch, one of skill in the art in possession of the present disclosurewill appreciate how the output of the optical directional coupler device1600 conserves optical power of the light input, as compared to the 2×1single-mode Y-junction optical waveguide 1000 discussed above withreference to FIG. 10 that outputs light with approximately half thepower of light input.

Thus, with reference back to FIG. 14B, one of skill in the art inpossession of the present disclosure will appreciate how the firstoptical signals produced at the first optical transmit connection 406 aand the second optical signals produced at the second optical transmitconnection 406 b by the quadrature optical modulator subsystem 404 mayhave identical optical power and may be encoded with identicalinformation (i.e., in the I quadrature and Q quadrature discussedabove), but with that information encoded with different phaserelationships in the first optical signals and the second opticalsignals. Furthermore, with reference to the discussion of theconventional IC-TROSA device 800 with regard to FIG. 11 , and one ofskill in the art in possession of the present disclosure will recognizethat the hub IC-TROSA device 400 operates to transmit the sameinformation as the conventional IC-TROSA device 800, but without thewaste light 1100 produced by 2×1 single-mode Y-junction opticalwaveguide 804 a, thus effectively doubling the optical power of theoptical signals used to transmit that information relative to theconventional IC-TROSA device 800. As will be appreciated by one of skillin the art in possession of the present disclosure, the generation ofthe first optical signals and the second optical signals by the hubcoherent optical transceiver device 400 discussed above is applicable toall types of coherent data transmission modulation formats.

The method 1300 then proceeds to block 1304 where the hub coherentoptical transceiver device transmits the first optical signals via afirst port, and transmits the second optical signals via a second port.With reference to FIGS. 14A and 14B, in an embodiment of block 1304, thehub IC-TROSA device 208 may perform first optical signal transmissionoperations 1406 that include transmitting the first optical signalsdiscussed above via the first optical transmit connection 210 a to thefirst hub optical network connector 210, and may perform second opticalsignal transmission operations 1408 that include transmitting the secondoptical signals discussed above via the second optical transmitconnection 212 a to the second hub optical network connector 212. Withreference to FIG. 17A, in an embodiment of block 1304, the first opticalsignal transmission operations 1406 may include transmitting the firstoptical signals discussed above via the first hub optical networkconnector 210 and through the PON 604 such that it is received by thesubscriber coherent optical transceiver device 300 connected to each ofthe subscriber devices 602 a. With reference to FIG. 17B, in anembodiment of block 1304, the second optical signal transmissionoperations 1408 may include transmitting the second optical signalsdiscussed above via the second hub optical network connector 212 andthrough the PON 606 such that it is received by subscriber coherentoptical transceiver device 300 connected to each of the subscriberdevices 602 b.

The method 1300 then proceeds to block 1306 where subscriber coherentoptical transceiver devices receive optical signals from the hubcoherent optical transceiver device. With reference to FIG. 18 , in anembodiment of block 1306 and in response to the subscriber coherentoptical transceiver device 300 connected to any of the subscriberdevices 602 a and 602 b receiving optical signals from the hub coherentoptical transceiver device 200 on the hub device 600, the subscriberoptical network connector 310 on the subscriber coherent opticaltransceiver device 300 may perform optical signal transmissionoperations 1800 that include transmitting the optical signals to thesubscriber IC-TROSA device 308 via the optical receive connection 310 b.As discussed above, in some embodiments, the subscriber coherent opticaltransceiver device 300 may be a conventional subscriber coherent opticaltransceiver device with a conventional subscriber IC-TROSA device 308and a subscriber signal processing engine 304 configured according tothe teachings of the present disclosure, and in such embodiments, thesubscriber IC-TROSA device 308 may operate to perform conventionalIC-TROSA device optical-to-electrical signal conversion operations toconvert the optical signals received from the hub coherent opticaltransceiver device 200 to analog electrical signals, and then performelectrical signal transmission operations 1802 that include transmittingthe electrical signals to the subscriber signal processing engine 304via the data input connection 304 d.

However, as also discussed above, in other embodiments the subscribercoherent optical transceiver device 300 may be configured similarly tothe hub coherent optical transceiver device 200 described herein (i.e.,with similar IC-TROSA devices). As such, while the operation of thesubscriber coherent optical transceiver device 300 according to thoseembodiments is not described in detail herein, one of skill in the artin possession of the present disclosure will appreciate that, in suchembodiments, the subscriber IC-TROSA device 308 in the subscribercoherent optical transceiver device 300 may perform the same signalprocessing operations discussed below on optical signals received via afirst optical receive connection (while its second optical receiveconnection will remain unused).

The method 1300 then proceeds to decision block 1308 where it isdetermined whether the subscriber coherent optical transceiver device iscoupled to the first port or the second port on the hub coherent opticaltransceiver device. In an embodiment, at decision block 1308, thesubscriber signal processing engine 304 may performoptical-signal-receiving-configuration determination operations thatinclude determining whether the subscriber coherent optical transceiverdevice 300 is configured to receive optical signals via the first huboptical network connector 210 on the hub coherent optical transceiverdevice 200 connected to the hub device 600, or the second hub opticalnetwork connector 212 on the hub coherent optical transceiver device 200connected to the hub device 600.

As discussed above, the first optical signals transmitted as part of thefirst optical signal transmission operations 1406 and the second opticalsignals transmitted as part of the second optical signal transmissionoperations 1408 by the hub IC-TROSA device 400 are encoded withidentical information (i.e., in the I quadrature and Q quadraturediscussed above), but with that information encoded with different phaserelationships in the first optical signals and the second opticalsignals. As such, one of skill in the art in possession of the presentdisclosure will appreciate that the subscriber coherent opticaltransceiver device 300 receiving either of those optical signals willneed to perform particular signal processing operations that are basedon the I/Q optical phase relationship of the information encoded thereinin order to correctly decode that information from those opticalsignals. As such, the knowledge of which hub optical network port on thehub coherent optical transceiver device 200 from which optical signalsare received may indicate the optical phase relationship of theinformation in those optical signals, and thus the signal processingoperations that are required to correctly decode those optical signals .As will be appreciated by one of skill in the art in possession of thepresent disclosure, the optical-signal-receiving-configurationdetermination operations of the present disclosure may be performed in avariety of manners that will fall within the scope of the presentdisclosure.

For example, in some embodiments theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 identifying, in adatabase that is accessible to the subscriber signal processing engine304 (e.g., in the subscriber coherent optical transceiver device 300, inthe hub device 600, or otherwise coupled to the subscriber signalprocessing engine 304), whether the subscriber coherent opticaltransceiver device 300 is coupled to the first hub optical networkconnector 210 on the hub coherent optical transceiver device 200connected to the hub device 600, or the second hub optical networkconnector 212 on the hub coherent optical transceiver device 200connected to the hub device 600. In a specific example, a networkadministrator, network operator, or other user may track the subscribercoherent optical transceiver devices 300/subscriber devices 602 acoupled to the first hub optical network connector 210 on the hubcoherent optical transceiver device 200 via the PON 604, and thesubscriber coherent optical transceiver devices 300/subscriber devices602 b coupled to the second hub optical network connector 212 on the hubcoherent optical transceiver device 200 via the PON 606, and may provideinformation in the database that is accessible to the subscriber signalprocessing engine 304 that identifies the connection of the subscribercoherent optical transceiver devices 300 to the first hub opticalnetwork connector 210 or the second hub optical network connector 212.

As such, in some embodiments of decision block 1308, theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 selecting, when thedatabase identifies that the subscriber coherent optical transceiverdevice 300 is coupled to the first hub optical network connector 210 onthe hub coherent optical transceiver device 200 connected to the hubdevice 600, first signal processing operations to perform on theelectrical signals received from the subscriber IC-TROSA device 308 viathe electrical signal transmission operations 1802. Similarly, theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 selecting, when thedatabase identifies that the subscriber coherent optical transceiverdevice 300 is coupled to the second hub optical network connector 212 onthe hub coherent optical transceiver device 200 connected to the hubdevice 600, second signal processing operations to perform on theelectrical signals received from the subscriber IC-TROSA device 308 viathe electrical signal transmission operations 1802.

In another example, in some embodiments theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 receiving theoptical signals from the hub coherent optical transceiver device 200connected to the hub device 600 and either: 1) performing first signalprocessing operations on those optical signals (discussed in furtherdetail below) and determining that the first signal processingoperations have correctly decoded those optical signals, or 2)performing second signal processing operations on those optical signalsand determining that the second signal processing operations haveincorrectly decoded the optical signals. In other words, if the firstsignal processing operations correctly decode received optical signalsor the second signal processing operations incorrectly decode receivedoptical signals, the subscriber signal processing engine 304 maydetermine that the subscriber coherent optical transceiver device 300 iscoupled to a particular hub optical network port on the hub coherentoptical transceiver device 200 connected to the hub device 600 thattransmits optical signals that are correctly decoded via the firstsignal processing operations.

Similarly, the optical-signal-receiving-configuration determinationoperations may include the subscriber signal processing engine 304receiving the optical signals from the hub coherent optical transceiverdevice 200 connected to the hub device 600 and either: 1) performingsecond signal processing operations on those optical signals (discussedin further detail below) and determining that the second signalprocessing operations have correctly decoded those optical signals, or2) performing first signal processing operations on those opticalsignals and determining that the first signal processing operations haveincorrectly decoded the optical signals. In other words, if the secondsignal processing operations correctly decode received optical signalsor the first signal processing operations incorrectly decode receivedoptical signals, the subscriber signal processing engine 304 maydetermine that the subscriber coherent optical transceiver device 300 iscoupled to a particular hub optical network port on the hub coherentoptical transceiver device 200 connected to the hub device 600 thattransmits optical signals that are correctly decoded via the secondsignal processing operations.

As such, in some embodiments of decision block 1308, theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 simply attempting toprocess the electrical signals with one of two available signalprocessing operations and determining whether those electrical signalshave been correctly or incorrectly decoded, which operates to implicitlyidentify the hub optical network port on the hub coherent opticaltransceiver device 200 connected to the hub device 600 to which thesubscriber coherent optical transceiver device 300 is connected. Thus,one of skill in the art in possession of the present disclosure willappreciate that the signal processing operations discussed below withreference to blocks 1310 and 1312 may be performed as part of decisionblock 1308 while remaining within the scope of the present disclosure aswell.

In yet another example, in some embodiments theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 receiving, during orprior to the method 1300, training communications from the hub coherentoptical transceiver device 200 and/or hub device 600 and, based on thetraining communications, determining whether the subscriber coherentoptical transceiver device 300 is coupled to the first hub opticalnetwork connector 210 or the second hub optical network connector 212 onthe hub coherent optical transceiver device 200 connected to the hubdevice 600. As such, during or prior to the method 1300, the subscribersignal processing engine 304 may be “trained” or otherwise configuredbased on which of the first hub optical network connector 210 or thesecond hub optical network connector 212 on the hub coherent opticaltransceiver device 200 connected to the hub device 600 it is connected.

Thus, in some embodiments of decision block 1308, theoptical-signal-receiving-configuration determination operations mayinclude the subscriber signal processing engine 304 selecting, inresponse to the training identifying that the subscriber coherentoptical transceiver device 300 is coupled to the first hub opticalnetwork connector 210 on the hub coherent optical transceiver device 200connected to the hub device 600, first signal processing operations toperform on the electrical signals received from the subscriber IC-TROSAdevice 308 via the electrical signal transmission operations 1802.Similarly, the optical-signal-receiving-configuration determinationoperations may include the subscriber signal processing engine 304selecting, in response to the training identifying that the subscribercoherent optical transceiver device 300 is coupled to the second huboptical network connector 212 on the hub coherent optical transceiverdevice 200 connected to the hub device 600, second signal processingoperations to perform on the electrical signals received from thesubscriber IC-TROSA device 308 via the electrical signal transmissionoperations 1802. However, while three specific techniques for performingthe optical-signal-receiving-configuration determination operations havebeen described, one of skill in the art in possession of the presentdisclosure will appreciate that the subscriber signal processing engine304 may be configured to determine whether the subscriber coherentoptical transceiver device 300 is coupled to the first hub opticalnetwork connector 210 or the second hub optical network connector 212 onthe hub coherent optical transceiver device 200 using other techniquesthat will fall within the scope of the present disclosure as well.

If, at decision block 1306, it is determined that the subscribercoherent optical transceiver device is coupled to the first port on thehub coherent optical transceiver device, the method 1300 proceeds toblock 1310 where the subscriber coherent optical transceiver deviceperforms first signal processing operations on the first opticalsignals. In an embodiment in which the first optical signals transmittedas part of the first optical signal transmission operations 1406 are thesame as optical signals transmitted by the conventional hub IC-TROSAdevice 800 discussed above with reference to FIG. 15 , at block 1310 thesubscriber IC-TROSA device 308 may perform conventional signalprocessing operations in order to decode the first optical signals,discussed in further detail below. If at decision block 1306, it isdetermined that subscriber coherent optical transceiver device iscoupled to the second port on the hub coherent optical transceiverdevice, the method 1300 proceeds to block 1312 where the subscribercoherent optical transceiver device performs second signal processingoperations on the second optical signals, discussed in further detailbelow.

A brief discussion of the conventional signal processing operationsreferenced above is provided below for purposes of highlighting thesignal processing operations performed according to the teachings of thepresent disclosure. With reference to FIG. 19 , the IC-TROSA receivesubsystem 806 in the conventional hub IC-TROSA device 800 discussedabove with reference to FIG. 8 is illustrated with the single opticalreceive connection 806 b configured to receive light that includes areceiver laser source electrical field, E_(St), and which is describedby the following equation:

E_(Sr) = E_(Sr)⁰e^(i(ω_(Sr)t + φ_(Sr)))(sin [φ₁(t)] + isin [φ_(Q)(t)])

Where

E_(Sr)⁰

is the (positive, real) signal amplitude, ω_(Sr) is the (angular)optical frequency of the signal and φ_(Sr) is the optical phase of thesignal. In a specific example in which optical signals are broadband16-QAM modulated optical signals, sin[φ_(l)(t)] and sin[φ_(Q)(t)]represent the 4-PAM signal levels of the I and Q quadratures. However,more general embodiments (e.g., when the signal is modulated with mdiscrete sub-carriers each offset from the signal optical carrier ω_(Sr)by ω_(Srm)), then sin[φ_(l)(t)] and sin[φ_(Q)(t)] represent complexwaveforms which are the inverse Fourier transforms of the frequencydomain signal.

The IC-TROSA receive subsystem 806 in the conventional hub IC-TROSAdevice 800 may then mix the optical signals with a light wave having thereceiver local oscillator electrical field E_(L) described by thefollowing equation:

E_(L) = E_(L)⁰e^(i(ω_(L)t + φ_(L)))

where

E_(L)⁰

is its (positive, real) amplitude, ω_(L) is its (angular) opticalfrequency, and φ_(L) is its optical phase.

In the most general embodiment, ω_(Sr) ≠ ω_(L), and one of skill in theart in possession of the present disclosure will recognize the mixingwill yield the following:

$\begin{array}{l}{\frac{E_{Sr}^{*}E_{L}}{E_{Sr}^{0}E_{L}^{0}} = \left( {\sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)} \\\left( {+ \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{S} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right) \\{+ i\left( {- \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\cos\left\lbrack {\varphi_{Q}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)} \\\left( {+ \sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)\end{array}$

As will be appreciated by one of skill in the art in possession of thepresent disclosure, the subscriber signal processing engine 304 may beconfigured to recover the optical phase of the signal φ_(Sr), and alignthat to the optical phase of the local oscillator φ_(L), effectivelyrendering φ_(L) - φ_(Sr) = 0.

As such, with reference back to FIG. 19 , an example of the conventionalhub IC-TROSA device 800 mixing of optical signals provided by light thatincludes a receiver laser source electrical field E_(Sr) with the lightwaves having the receiver local oscillator electrical field E_(L) toprovide electrical signals is illustrated using a table 1900. As can beseen, the table 1900 identifies optical signals 1, 2, 3, and 4 that areprovided to respective photodiodes (PDs) in the conventional hubIC-TROSA device 800, as well as electrical signals A and B that areoutput by respective differential amplifiers. As will be appreciated byone of skill in the art in possession of the present disclosure, theE_(PD) column in the table 1900 identifies the optical field at therespective PD receiving each of the optical signals 1, 2, 3, and 4, andthe i_(PD)/n column in the table 1900 identifies the photo-currentproduced at the respective PD receiving each of the optical signals 1,2, 3, and 4 in response to the optical field E_(PD).

The table 1900 illustrates how the output of one of the differentialamplifiers in the conventional hub IC-TROSA device 800 will be theelectrical signal A with a value proportional to Re[E_(Sr)E_(L)], whilethe output of the other of the differential amplifiers in theconventional hub IC-TROSA device 800 will be the electrical signal Bwith a value proportional to

−Im[E_(Sr)^(*)E_(L)],

with the values

Re[E_(Sr)^(*)E_(L)]

and

Im[E_(Sr)^(*)E_(L)],

described by the equations below:

$\begin{array}{l}{{Re}\left\lbrack {E_{Sr}^{*}E_{L}} \right\rbrack =} \\{E_{Sr}^{0}E_{L}^{0}\left( {\sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\cos\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack + \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\sin\left( {\omega_{L} - \omega_{Sr}} \right)t} \right)}\end{array}$

$\begin{array}{l}{{Im}\left\lbrack {E_{Sr}^{*}E_{L}} \right\rbrack =} \\{E_{Sr}^{0}E_{L}^{0}\left( {- \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\cos\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack +} \right)} \\\left( {\sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\sin\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)\end{array}$

As will be appreciated by one of skill in the art in possession of thepresent disclosure, in embodiments in which the local oscillator istuned such that ω_(Sr) = ω_(L), and the hub IC-TROSA device istransmitting broadband 16-QAM modulated signals, the voltages measuredat the outputs of the differential amplifiers are proportional to the4-PAM signal levels of the I and Q quadratures of a data-carrying 16-QAMconstellation. In more general embodiments in which ω_(Sr) ≠ ω_(L),signal processing techniques may be used to recover the originalwaveforms sin[φ_(l)(t)] and sin[φ_(Q)(t)].

With reference to FIGS. 18 and 19 , when the conventional IC-TROSAreceive subsystem 806 is provided in the subscriber IC-TROSA device 308it may be configured to receive light that includes the receiver lasersource electrical field E_(Sr), which as discussed above may be providedas part of the optical signals received as part of the optical signaltransmission operations 1800, and which may be proportional to thefollowing equation:

E_(Sr) = E_(Sr)⁰e^(i(ω_(Sr)t + φ_(Sr)))(sin [φ_(I)(t)]) ± isin [φ_(Q)(t)]

Where

E_(Sr)⁰

is the (real) signal amplitude, ω_(Sr) is the (angular) opticalfrequency of the signal, φ_(Sr) is the optical phase of the signal, andthe sign ± depends on the origin of the signal (e.g., “+” for the firstoptical signals, and “-” for the second optical signals discussedabove).

The IC-TROSA receive subsystem 806 in the subscriber IC-TROSA device 308may then mix the optical signals with the light wave having the receiverlocal oscillator electrical field E_(L) described by the followingequation:

E_(L) = E_(L)⁰e^(i(ω_(L)t + φ_(L)))

One of skill in the art in possession of the present disclosure willrecognize the mixing will yield the following:

$\begin{array}{l}{\frac{E_{Sr}^{*}E_{L}}{E_{Sr}^{0}E_{L}^{0}} = \left( {\sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)} \\\left( {\pm \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right) \\{+ i\left( {\mp \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)} \\\left( {+ \sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr} + \left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)\end{array}$

As will be appreciated by one of skill in the art in possession of thepresent disclosure, the subscriber signal processing engine 304 may beconfigured to recover the optical phase of the signals φ_(Sr), and alignthat to the optical phase of the local oscillator φ_(L), effectivelyrendering φ_(L) - φ_(Sr) = 0.

As such, with reference back to the table 1900 in FIG. 19 , the outputof one of the differential amplifiers in the IC-TROSA receive subsystem806 in the subscriber IC-TROSA device 308 will be the electrical signalA with a value proportional to

Re[E_(Sr)^(*)E_(L)],

while the output of the other of the differential amplifiers in theconventional hub IC-TROSA device 800 will be the electrical signal Bwith a value proportional to

−Im[E_(Sr)^(*)E_(L)],

with the values

Re[E_(Sr)^(*)E_(L)],

and

Im[E_(Sr)^(*)E_(L)],

described by the equations below

$\begin{array}{l}{{Re}\left\lbrack {E_{Sr}^{*}E_{L}} \right\rbrack = E_{Sr}^{0}E_{L}^{0}\left( {\sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\cos\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack \pm} \right)} \\\left( {\sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\sin\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)\end{array}$

$\begin{array}{l}{{Im}\left\lbrack {E_{Sr}^{*}E_{L}} \right\rbrack = E_{Sr}^{0}E_{L}^{0}\left( {\mp \sin\left\lbrack {\varphi_{Q}(t)} \right\rbrack\cos\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack +} \right)} \\\left( {\sin\left\lbrack {\varphi_{I}(t)} \right\rbrack\sin\left\lbrack {\left( {\omega_{L} - \omega_{Sr}} \right)t} \right\rbrack} \right)\end{array}$

As will be appreciated by one of skill in the art in possession of thepresent disclosure, conventional signal processing operations (e.g., thefirst signal processing operations discussed above) will provide for thecorrect decoding of the first optical signals transmitted from the firsthub optical network connector 210, as the values for

Re[E_(Sr)^(*)E_(L)]and =Im[E_(Sr)^(*)E_(L)]

are the same as utilized by the IC-TROSA receive subsystem 806 in theconventional hub IC-TROSA device 800. However, such conventional signalprocessing operations will incorrectly decode the second optical signalstransmitted from the second hub optical network connector 212, and mustbe modified based on the knowledge of which hub optical network port thesubscriber coherent optical transceiver device 300 is coupled to inorder to perform the second signal processing operations discussedabove, and one of skill in the art in possession of the presentdisclosure will recognize how the second signal processing operationswould be configured to correctly decode such optical signals.

Thus, systems and methods have been described that include a hubIC-TROSA device with an optical directional coupler device thatsubstantially eliminates optical signal loss produced by conventionalhub IC-TROSA devices while providing dual optical transmit connectionsthat allow the hub IC-TROSA device to transmit two optical signals (viathe respective transmit connections) to different point-to-multipointoptical networks. For example, the hub IC-TROSA point-to-multipointoptical network system of the present disclosure may include apoint-to-multipoint optical network that is coupled to subscriberdevices, and that is coupled to a hub device via a hub IC-TROSA deviceincluded in a hub coherent optical transceiver device coupled to the hubdevice. The hub IC-TROSA device includes a quadrature optical modulatorsubsystem, and an optical directional coupler device in the quadratureoptical modulator subsystem provides a first transmit connection and asecond transmit connection to the point-to-multipoint optical network.The optical directional coupler device receives first optical signalsfrom the quadrature optical modulator subsystem and transmits them viathe first transmit connection to a first subset of the subscriberdevices via the point-to-multipoint optical network, and receives secondoptical signals from the quadrature optical modulator subsystem andtransmits them via the second transmit connection to a second subset ofthe subscriber devices via the point-to-multipoint optical network.

Referring now to FIG. 20 , an embodiment of a method 2000 fortransmitting data via a point-to-multipoint optical network isillustrated. As discussed below, the systems and methods of the presentdisclosure include a hub IC-TROSA device with an optical directionalcoupler device that substantially eliminates optical signal lossproduced by conventional hub IC-TROSA devices while providing dualoptical receive connections that allow the hub IC-TROSA device toreceive two optical signals (via the respective receive connections)from different point-to-multipoint optical networks. As discussed below,the hub IC-TROSA device of the present disclosure increases the distanceover which optical signals may be received, or increases the number ofsubscriber devices from optical signals may be received over aparticular distance, via point-to-multipoint networks relative toconventional hub IC-TROSA devices.

The method 2000 begins at block 2002 where each subscriber coherentoptical transceiver device generates optical signals. With reference toFIGS. 6 and 21 , in an embodiment of block 2002, the subscriber devices602 a and/or 602 b may provide data (e.g., via electrical signals) tothe subscriber coherent optical transceiver devices 300 via thesubscriber device connector 306, and the subscriber device connector 306may perform data transmission operations 2100 that may includetransmitting the data (e.g., via electrical signals) through the datainput connection 304 a and to the subscriber signal processing engine304. Furthermore, the subscriber ITLA device(s) 312 may perform lightprovisioning operations 2102 by generating and transmitting light to thesubscriber IC-TROSA device 308. The subscriber signal processing engine304 may then utilize the data received via the data input connection 304a from the subscriber device connector 306 to perform optical signalgeneration operations 2104 that include transmitting optical signalgeneration commands (based on the data) to the subscriber IC-TROSAdevice 308.

FIG. 22 illustrates how each subscriber coherent optical transceiverdevices 300 connected to each subscriber devices 602 a and the PON 604may transmit a first set of optical signals to the first hub opticalnetwork connector 210 on the hub coherent optical transceiver device 200connected to the hub device 600, and the subscriber coherent opticaltransceiver devices 300 connected to the subscriber devices 602 b andthe PON 606 may transmit second set of optical signals to the second huboptical network connector 212 on the hub coherent optical transceiverdevice 200 connected to the hub device 600.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, each subscriber coherent optical transceiver devices300 may be configured to determine which signal processing operations toperform in a manner similar to that described above with regard todecision block 1308 of the method 1300. Furthermore, one of skill in theart in possession of the present disclosure will recognize that thegeneration of the first set of optical signals and the second set ofoptical signals by the subscriber coherent optical transceiver devices300 discussed above is applicable when the hub optical transceiver candifferentiate optical signals from the various subscriber coherentoptical transceiver devices 300 by sub-carrier multiple access (SCMA),time-division multiple access (TDMA), or hybrid multiplexing techniquesthat would be apparent to one of skill in the art in possession of thepresent disclosure.

The method 2000 then proceeds to block 2004 where each subscribercoherent optical transceiver device transmits optical signals to a hubcoherent optical transceiver device. With reference to FIG. 21 , in anembodiment of block 2004, each subscriber IC-TROSA device 308 mayperform optical signal transmission operations 2106 that includetransmitting the optical signals generated at block 2002 via the opticaltransmit connection 310 a and to the subscriber optical networkconnector 310.

The method 2000 then proceeds to decision block 2006 where the method2000 proceeds depending on whether the hub coherent optical transceiverdevice receives the first set of optical signals or the second set ofoptical signals from the subscriber coherent optical transceiverdevices. With reference to FIG. 23 , in an embodiment of block 2006, thefirst hub optical network connector 210 may perform optical signaltransmission operations 2300 that include transmitting the first set ofoptical signals to the hub IC-TROSA device 208 via the first opticalreceive connection 210 b, while the second hub optical network connector212 may perform optical signal transmission operations 2302 that includetransmitting the second set of optical signals to the hub IC-TROSAdevice 208 via the second optical receive connection 212 b.

With reference to FIG. 24 , in an embodiment, the first set of opticalsignals may include light with receiver laser source electrical fieldE_(Sr1i), and the second set of optical signals may include light withreceiver laser source electrical field E_(Sr2j), each described by thefollowing equations:

E_(Sr1i) = E_(Sr1i)⁰e^(i(ω_(Sr1i)t + φ_(Sr1i)))(sin [φ_(I1i)(t)] + isin [φ_(Q1i)(t)])

E_(Sr2j) = E_(Sr2j)⁰e^(i(ω_(Sr2j)t + φ_(Sr2j)))(sin [φ_(I2j)(t)] + isin [φ_(Q2j)(t)])

where i refers to the signal originating at the i^(th) subscriberterminal on the first network, and j refers to the signal originating atthe j^(th) subscriber terminal on the second network. In addition, oneof skill in the art in possession of the present disclosure willappreciate that the “1” subscript indicates that the associated lightwas received at the first optical receive connection 210 b, while the“2” subscript indicates that the associated light was received at thesecond optical receive connection 212 b.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, in the case of a TDMA coherent PON, only a singleupstream optical signal packet from a single distinct subscriber isreceived (and decoded) by the hub coherent transceiver at any one time.However, in the case of a SCMA coherent PON, a multitude of opticalsubcarriers are received and decoded simultaneously

As will be appreciated by one of skill in the art in possession of thepresent disclosure, each E_(Sr1i) and E_(Sr2j) originate from differentsubscriber coherent optical transceiver devices so generally opticalphases and frequencies are different (φ_(Sr1i) ≠ φ_(Sr1k) ≠ φ_(Sr2j) ≠φ_(Sr2n) and (ω_(Sr1i) ≠ ω_(Sr1k) ≠ ω_(Sr2j) ≠ ω_(Sr2n)) and the digitalsignal processing operations performed by the hub signal processingengine 204 may be configured to distinguish such signals from differentsubscriber coherent optical transceiver devices depending on whether thecoherent PON upon which they are received uses TDMA, SCMA, combinationsthereof, or other transmission technologies known in the art.

For example, considering a coherent single-carrier PON using TDMAtransmission technology, the optical frequency and phase of a receivedsignal may vary depending on timeslot and subscriber source, and thedigital signal processing operations performed by the hub signalprocessing engine 204 may be configured to effectively manage suchreceived signals. To provide a specific example, the signal may bereceived by the hub coherent optical transceiver device 200 and mayenter the hub IC-TROSA device 400 through either the first opticalreceive connection 410 a or the second optical receive connection 410 b.The digital signal processing operations performed by the hub signalprocessing engine 204 (and a hub coherent optical transceiverMedia-Access Control [MAC]) will be aware of which subscriber coherentoptical transceiver device is assigned to the timeslot that is currentlybeing decoded, and may also know if the subscriber coherent opticaltransceiver device is in a first subscriber domain optically connectedto first optical receive connection 410 a, or in a second subscriberdomain optically connected to second optical receive connection 410 b.

In another example, considering a coherent multi-carrier SCMA coherentPON transmission technology, the optical frequency and phase of areceived optical subcarriers may vary depending on the subcarrierfrequency and the subscriber source, and the digital signal processingoperations performed by the hub signal processing engine 204 may beconfigured to effectively manage such received signals. To provide aspecific example, the signal may be received by the hub coherent opticaltransceiver device 200 and may enter the hub IC-TROSA device 400 througheither the first optical receive connection 410 a or the second opticalreceive connection 410 b. The digital signal processing operationsperformed by the hub signal processing engine 204 will be aware of whichof the optical subcarriers is assigned to which subscriber coherentoptical transceiver device, and may also know if the subscriber coherentoptical transceiver device is in a first subscriber domain opticallyconnected to first optical receive connection 410 a, or in a secondsubscriber domain optically connected to second optical receiveconnection 410 b.

The method 2000 then may proceed to block 2008 where the hub coherentoptical transceiver device performs first signals processing operationson the first set of optical signals, or to block 2010 where the hubcoherent optical transceiver device performs second signals processingoperations on the second set of optical signals. One of skill in the artin possession of the present disclosure will appreciate how operationsassociated with blocks 2010 and 2010 may be performed sequentially inthe case of a TDMA coherent PON, or simultaneously in the case of a SCMAcoherent PON, for example. With reference to FIG. 24 , in an embodimentof blocks 2008 and 2010 and as discussed above, the optical directionalcoupler device 408 b in the hub coherent optical transceiver device 400may be configured to receive light having the receiver local oscillatorelectrical field E_(L) provided by the hub ITLA device 214 at one of itsinputs, which may be described by the equation:

E_(L) = E_(L)⁰e^(i(ω_(i)t + φ_(i)))

As will be appreciated by one of skill in the art in possession of thepresent disclosure, the mixing provided by the hub coherent opticaltransceiver device 400 may yield the following nonvanishing terms at theelectrical output of the IC-TROSA:

$\begin{array}{l}{\frac{E_{Sr1i}^{*}E_{L}}{E_{Sr1i}^{0}E_{L}^{0}} = \left( {\sin\left\lbrack {\varphi_{I1i}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr1i} + \left( {\omega_{L} - \omega_{Sr1i}} \right)t} \right\rbrack} \right)} \\\left( {+ \sin\left\lbrack {\varphi_{Q1i}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr1i} + \left( {\omega_{L} - \omega_{Sr1i}} \right)t} \right\rbrack} \right) \\{+ i\left( {- \sin\left\lbrack {\varphi_{Q1i}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr1i} + \left( {\omega_{L} - \omega_{Sr1i}} \right)t} \right\rbrack} \right)} \\\left( {+ \sin\left\lbrack {\varphi_{I1i}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr1i} + \left( {\omega_{L} - \omega_{Sr1i}} \right)t} \right\rbrack} \right) \\\text{and}\end{array}$

$\begin{array}{l}{\frac{E_{Sr2j}^{*}E_{L}}{E_{Sr2j}^{0}E_{L}^{0}} =} \\\left( {\sin\left\lbrack {\varphi_{Q2j}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr2j} + \left( {\omega_{L} - \omega_{Sr2j}} \right)t} \right\rbrack} \right) \\\left( {+ \sin\left\lbrack {\varphi_{I2j}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr2j} + \left( {\omega_{L} - \omega_{Sr2j}} \right)} \right\rbrack t} \right) \\{+ i\left( {- \sin\left\lbrack {\varphi_{Q2j}(t)} \right\rbrack\cos\left\lbrack {\varphi_{L} - \varphi_{Sr2j} + \left( {\omega_{L} - \omega_{Sr2j}} \right)t} \right\rbrack} \right)} \\\left( {+ \sin\left\lbrack {\varphi_{I2j}(t)} \right\rbrack\sin\left\lbrack {\varphi_{L} - \varphi_{Sr2j} + \left( {\omega_{L} - \omega_{Sr2j}} \right)t} \right\rbrack} \right)\end{array}$

As will be appreciated by one of skill in the art in possession of thepresent disclosure, in the case of the TDMA coherent PON, the hub signalprocessing engine 204 may be configured to recover the optical phase ofeach upstream signal packet carrying the signals φ_(Sr1l) and φ_(Sr2j),align it to the optical phase of the local oscillator φ_(L), effectivelyrendering φ_(L) - φ_(Sr1l) = φ_(L) ― φ_(Sr2j) = 0.

As such, with reference back to FIG. 24 , an example of the hub IC-TROSAdevice 400 mixing optical signals having light that includes a receiversignal electrical fields E_(Sr1i) and E_(Sr2j) with the light waveshaving the receiver local oscillator electrical field E_(L) to provideelectrical signals is illustrated using a table 2400. As can be seen,the table 2400 identifies optical signals 1, 2, 3, and 4 that areprovided to respective PDs 408 e, 408 h, 408 k, and 408 n in the hubIC-TROSA device 400, as well as electrical signals A and B that areoutput by respective differential amplifiers 408 g and 408 m. Asdiscussed above, the E_(PD) column in the table 2400 identifies theoptical field at the respective PD receiving each of the optical signals1, 2, 3, and 4, and the i_(PD)/η column in the table 2400 identifies thephoto-current produced at the respective PD receiving each of theoptical signals 1, 2, 3, and 4 in response to the optical field E_(PD).

With reference to both FIG. 24 and FIG. 6 , one of skill in the art inpossession of the present disclosure will recognize how, for signalsreceived from subscriber coherent optical transceiver devices 300connected to the PON 604, the output of one of the differentialamplifiers in the hub IC-TROSA device 400 will be the electrical signalA that is proportional to +Re[E_(Sr1i)E_(L)], while the output of theother of the differential amplifiers in the hub IC-TROSA device 400 willbe the electrical signal B that is proportional to -Im[E_(Sr1i)E_(L)].As will be appreciated by one of skill in the art in possession of thepresent disclosure, such signals may be decoded using the conventionalsignal processing operations described above with reference to FIG. 19 .

However, again with reference to FIG. 24 and FIG. 6 , one of skill inthe art in possession of the present disclosure will also recognize how,for signals received from subscriber coherent optical transceiverdevices 300 connected to the PON 606, the output of one of thedifferential amplifiers in the hub IC-TROSA device 400 will be theelectrical signal A that is proportional to +Im[E_(Sr2j)E_(L)]while theoutput of the other of the differential amplifiers in the hub IC-TROSAdevice 400 will be the electrical signal B that is proportional to-Re[E_(Sr2j)E_(L)].

With reference to FIG. 24 , as will be appreciated by one of skill inthe art in possession of the present disclosure, for signals receivedfrom subscriber coherent optical transceiver devices 300 connected tothe PON 606, the hub signal processing engine 204 may performconventional operations while interpreting the inverse of the voltagefrom differential amplifier 408 g as being from differential amplifier408 m, and interpreting the inverse of the voltage from differentialamplifier 408 m as being from differential amplifier 408 g. Furthermore,other elements of the digital signal processing operations performed bythe hub signal processing engine 204 including chromatic dispersioncompensation, IQ skew compensation, carrier recovery, polarization modedispersion compensation, polarization tracking and demultiplexing,frequency offset estimation, as well as others, may be modified forsignals received via the second optical transceiver connection 410 b onthe hub IC-TROSA device 400.

While the discussion above is specific to a coherent single-carrier PONusing TDMA transmission technology, other PONs using other transmissiontechnologies will fall within the scope of the present disclosure aswell. For example, consider a coherent multi-carrier PON using SCMAtransmission technology in which the hub coherent optical transceiverdevice will receive signals simultaneously from different subscribercoherent optical transceiver devices operating on different opticalsubcarriers, which one of skill in the art in possession of the presentdisclosure will recognize presents challenges because the optical signalfrom any particular subscriber coherent optical transceiver devices mayhave a distinct optical carrier frequency and phase, as well asdistinct, distance dependent, optical impairments. However, one of skillin the art in possession of the present disclosure will also appreciatehow simultaneous optical carrier and phase recovery techniques for eachsignal and/or subcarrier may be employed to address such challenges(e.g., via the use of frequency locking each subscriber coherent opticaltransceiver device controlled by the hub coherent optical transceiverdevice). [D. Welch, et al., “Point-to-Multipoint Optical Networks UsingCoherent Digital Subcarriers,” Journal of Lightwave Technology, vol. 39,no. 16, pp. 5232-5247, 2021 AND H. Sun, et al., “800G DSP ASIC DesignUsing Probabilistic Shaping and Digital Sub-Carrier Multiplexing,”Journal of Lightwave Technology, vol. 38, no. 17 pp. 4744-4756 (2020).]As with the coherent single-carrier PONs using TDMA discussed above,elements of the digital signal processing operations performed by thehub signal processing engine 204 used with coherent multi-carrier PONsusing SCMA transmission technology may include chromatic dispersioncompensation, IQ skew compensation, carrier recovery, polarization modedispersion compensation, polarization tracking and demultiplexing,frequency offset estimation, as well as others, may be modified forsignals received via the second optical transceiver connection 410 b onthe hub IC-TROSA device 400.

As would be appreciated by one of skill in the art in possession of thepresent disclosure, the systems and methods of the present disclosuremay require (e.g., in the case of a n SCMA coherent PON) that theoptical subcarrier frequencies assigned to subscriber devices on a firstnetwork connected to the hub device not be mirror frequencies (e.g., twofrequencies ω₁ and ω₂ where [ω₁ ― ω₀ = ω₀ ― ω₂] or [ω₂ ― ω₀ = ω₀ ― ω₁]where ω₀ is the (angular) optical frequency of the hub local oscillator)of the optical subcarrier frequencies assigned to subscriber devices ona second network connected to the hub device. While conventional SCMApoint-to-multipoint optical networks do not constrain the assignment ofoptical subcarrier frequencies to subscriber devices, the techniquesdescribed herein may experience interference between subscriber devicesthat are assigned with mirror frequencies in the different networks. Assuch, the hub device may perform optical subcarrier frequencyassignments to ensure that optical subcarrier frequencies assigned tosubscriber devices on the first network connected to the hub device arenot mirror frequencies of the optical subcarrier frequencies assigned tosubscriber devices on a second network connected to the hub device.

With reference to FIG. 25 , blocks 2008 and 2010 may alternatively beperformed using the hub IC-TROSA receive subsystem provided by theoptical hybrid mixer subsystem 502 in the hub IC-TROSA device 500discussed above with reference to FIG. 5 . As such, the optical hybridmixer subsystem 502 may receive the first set of optical signals thatinclude light with received electrical field E_(Sr1i), and the secondset of optical signals that include light with received electrical fieldE_(Sr2j), with an arbitrary π/4 radian phase shift provided to each ofthe corresponding signals (in order to simplify the math involved) suchthat the first set of optical signals and second set of optical signalsare described by E_(Sr1i)e^(iπ/4) and E_(Sr2j)e^(iπ/4), respectively. Aswill be appreciated by one of skill in the art in possession of thepresent disclosure, using the known phase shifts provided by MMI devicesand techniques similar to those used to calculate the electrical signalsoutput by the optical hybrid mixer subsystem 408 with reference to FIG.24 , the output of the differential amplifiers 502 k and 502 tidentified in the table 2500 in FIG. 25 may be determined. Furthermore,one of skill in the art in possession of the present disclosure willappreciate how corresponding modifications to the subscriber signalprocessing engine 204 and the hub signal processing engine 204 may bederived based on the results illustrated in FIG. 25 in order to ensurecorresponding optical signals are encoded/transmitted andreceived/decoded correctly.

With reference to the IC-TROSA transmit subsystem 804 in theconventional IC-TROSA device 800 discussed above with reference to FIG.8 and its coupling to the subscriber devices 900 via the PON 902discussed above with reference to FIG. 9 , some benefits of the systemsand methods of the present disclosure may be appreciated. For example,with reference to the quadrature optical modulator subsystem 404 in thehub IC-TROSA device 400 discussed above with reference to FIG. 4 ,consider the coupling of the hub coherent optical transceiver device 200to the subscriber coherent optical transceiver devices 300 illustratedin FIG. 26 , with eight subscriber coherent optical transceiver devices300 coupled to the first hub optical network connector 210 on the hubcoherent optical transceiver device 200 via a first PON 2600a, and eightsubscriber coherent optical transceiver devices 300 coupled to thesecond hub optical network connector 212 on the hub coherent opticaltransceiver device 200 via a second PON 2600b.

As will be appreciated by one of skill in the art in possession of thepresent disclosure, the optical directional coupler device 404 n in thequadrature optical modulator subsystem 404 allows for the removal of the1×2 single-mode Y-junction optical waveguides 902 a required to allowthe conventional hub coherent optical transceiver device 800 to transmitoptical signals to the sixteen subscriber devices 900. Similarly, theoptical directional coupler device 408 a in the optical hybrid mixersubsystem 408 allows for the removal of the 1×2 single-mode Y-junctionoptical waveguides 902 a required to allow the conventional hub coherentoptical transceiver device 800 to receive optical signals from thesixteen subscriber devices 900. As will be appreciated by one of skillin the art in possession of the present disclosure, the removal of the1×2 single-mode Y-junction optical waveguides 902 a reduces light powerloss experienced in the system illustrated in FIG. 9 by 3 decibels (dB),which at an approximate optical fiber loss ratio of 0.2 dB/km at 1550 nmoptical wavelengths, operates to increase the distance the hub coherentoptical transceiver device 400 can transmit optical signals at aparticular power to its sixteen subscriber coherent optical transceiverdevices 300/subscriber devices by approximately 15 km relative to thehub coherent optical transceiver device 800 and its subscriber devices900. Alternatively, rather than increase the optical signal transmissiondistance, an additional 1×2 single-mode Y-junction optical waveguide maybe added to the PONs 2600a and 2600b to double the number of subscribercoherent optical transceiver devices 300/subscriber device supported.

Referring now to FIG. 27 , the conventional IC-TROSA device 800discussed above with reference to FIG. 8 is illustrated coupled to thesubscriber devices 900 via a PON 2700 that includes a plurality of 1×2single-mode Y-junction optical waveguides 2702a, 2702b, 2702c, 2702 d,2702 e, 2702 f, and 2702 g that allow the conventional IC-TROSA device800 to transmit optical signals having a threshold optical power level aparticular distance to the subscriber devices 900. With reference to thequadrature optical modulator subsystem 404 in the hub IC-TROSA device400 discussed above with reference to FIG. 4 , consider the coupling ofthe hub coherent optical transceiver device 200 to the subscribercoherent optical transceiver devices 300 illustrated in FIG. 28 , witheight subscriber coherent optical transceiver devices 300 coupled to thefirst hub optical network connector 210 on the hub coherent opticaltransceiver device 200 via a first PON 2800 a, and eight subscribercoherent optical transceiver devices 300 coupled to the second huboptical network connector 212 on the hub coherent optical transceiverdevice 200 via a second PON 2800b.

As discussed above, the optical directional coupler device 404 n in thequadrature optical modulator subsystem 404 allows the hub coherentoptical transceiver device 200 to transmit first optical signals havingthe threshold optical power level discussed above the particulardistance discussed above to the eight subscriber coherent opticaltransceiver devices 300 coupled to the first hub optical networkconnector 210 on the hub coherent optical transceiver device 200 via afirst PON 2800 a, and transmit second optical signals having thethreshold optical power level discussed above the particular distancediscussed above to the eight subscriber coherent optical transceiverdevices 300 coupled to the second hub optical network connector 212 onthe hub coherent optical transceiver device 200 via a second PON 2800b.As will be appreciated by one of skill in the art in possession of thepresent disclosure, the use of the optical directional coupler device404 n in the quadrature optical modulator subsystem 404 increases (i.e.,doubles) the “overall optical link budget” by 3 decibels (dB), thusallowing the hub coherent optical transceiver device 200 to transmitoptical signals with the same optical power the same distance as thosetransmitted by the conventional hub coherent optical transceiver device800, but to twice as many subscriber coherent optical transceiverdevices. Alternatively, the hub coherent optical transceiver device 200may transmit optical signals with higher optical power the same distanceto eight subscriber coherent optical transceiver devices, thus providingthose optical signals with lower system bit error ratios in order toprovide a more robust network that can operate despite networkdegradation (e.g., due to aging effects on active and passive elementsin the network).

While specific benefits of the systems and methods of the presentdisclosure have been described above, one of skill in the art inpossession of the present disclosure will appreciate how the hubcoherent optical transceiver device 200 described herein provides avariety of other benefits as well. For example, in order to increase thedistance that optical signals may be transmitted by a 3 dB equivalent,or increase the number of subscriber devices to which optical signalsmay be transmitted by a 3 dB equivalent, two of the conventional hubcoherent optical transceiver devices 800 in a parallel configurationwould be required, thus doubling over power consumption, overall heatdissipation, overall cost, and the number of switch/router Ethernetports consumed (raising the possibility of stranded switch/routerbandwidth). As such, the hub coherent optical transceiver device 200operates to reduce power consumption, heat dissipation, cost, andswitch/router Ethernet ports consumed when transmitting optical signals,and one of skill in the art in possession of the present disclosure willappreciate how the configuration of the hub coherent optical transceiverdevice 200 will be associated with relatively minimal increases in powerconsumption, heat dissipation, and cost compared to the conventional hubcoherent optical transceiver device 800. Similarly, the subscribercoherent optical transceiver device 300 may require only a subscribersignal processing software upgrade, and thus will be associated withrelatively minimal increases in power consumption, heat dissipation, andcost compared to conventional subscriber coherent optical transceiverdevices as well.

Furthermore, one of skill in the art in possession of the presentdisclosure will appreciate how an additional transmit/receive port atthe hub can improve the carrier’s bandwidth utilization, as described in[D. Nesset, D. Piehler, K. Farrow and N. Parkin, “GPON SFP transceiverwith PIC based mode-coupled receiver,” 38^(th) European Conference andExhibition on Optical Communications (ECOC), 2012, London, UK, 2012,paper Tu.3.B.4.].

As discussed above, the hub IC-TROSA device 200 may include a pair ofquadrature optical modulator subsystems, and one of skill in the art inpossession of the present disclosure will appreciate how thosequadrature optical modulator subsystems may be configured in a varietyof manners. FIG. 29 illustrates one embodiment of such a hub IC-TROSAdevice 2900, which includes the quadrature optical modulator subsystem404 having the optical directional coupler device 404 n, as well as aquadrature optical modulator subsystem 2902 having an opticaldirectional coupler device 2904, with the quadrature optical modulatorsubsystem 2902 and the optical directional coupler device 2904 operatingsubstantially similarly as described above for the quadrature opticalmodulator subsystem 404 and the optical directional coupler device 404n. In the illustrated embodiment, each of the quadrature opticalmodulator subsystem 404 and the quadrature optical modulator subsystem2902 are configured to receive light via the same input 2906, while a2×1 Y-junction optical waveguide 2908 couples first outputs on each ofthe optical directional coupler device 404 n and the optical directionalcoupler device 2904 to a first optical transmit connection 2908 a, and a2×1 Y-junction optical waveguide 2910 couples second outputs on each ofthe optical directional coupler device 404 n and the optical directionalcoupler device 2904 to a second optical transmit connection 2910 a.

One of skill in the art in possession of the present disclosure willrecognize how the configuration of the hub IC-TROSA device 2900 replacestwo 2×1 Y-junction optical waveguides that would otherwise be includedin a conventional hub IC-TROSA device (e.g., with the opticaldirectional coupler devices 2908 and 2910), but with the first opticaltransmit connection 2908 a and the second optical transmit connection2910 a each provided by two 2×1 Y-junction optical waveguides. As such,the hub IC-TROSA device 2900 will reduce waste light relative to theconventional hub IC-TROSA devices by 3 dB, while also including dualoptical transmit ports (coupled to the first and second optical transmitconnections 2908 a and 2910 a) that each carry identical informationhaving quadratures that are at different optical phase relationships ineach of the optical signals. Furthermore, one of skill in the art inpossession of the present disclosure will recognize how the teachings ofthe present disclosure may be applied to modify optical signal encoding,decoding, and/or other signal processing operations in order to providefor the transmission of optical signals via the first and second opticaltransmit connections 2908 a and 2910 a as discussed above, as well asdecode those optical signals once received as discussed above as well.

With reference to FIG. 30 , an embodiment of a hub IC-TROSA device 3000is illustrated that is similar to the hub IC-TROSA device 2900, and thusincludes similar element numbers for similar components. However, the2×1 Y-junction optical waveguides 2908 and 2910 have been replaced by anoptical directional coupler device 3002 that couples first outputs oneach of the optical directional coupler device 404 n and the opticaldirectional coupler device 2904 to a first optical transmit connection3002 a and a second optical transmit connection 3002 b, and an opticaldirectional coupler device 3004 that couples second outputs on each ofthe optical directional coupler device 404 n and the optical directionalcoupler device 2904 to a third optical transmit connection 3004 a and afourth optical transmit connection 3004 b. One of skill in the art inpossession of the present disclosure will recognize how theconfiguration of the hub IC-TROSA device 3000 replaces the two 2×1Y-junction optical waveguides in the hub IC-TROSA device 2900 (e.g.,with the optical directional coupler devices 3002 and 3004). As such,the hub IC-TROSA device 3000 will reduce waste light relative to theconventional hub IC-TROSA devices by 6 dB, while also including fouroptical transmit ports (coupled to the first, second, third, and fourthoptical transmit connections 3002 a, 3002 b, 3004 a, and 3004 b) thateach carry identical information having quadratures that are atdifferent optical phase relationships in each of the optical signals.Furthermore, one of skill in the art in possession of the presentdisclosure will recognize how the teachings of the present disclosuremay be applied to modify optical signal encoding, decoding, and/or othersignal processing operations in order to provide for the transmission ofoptical signals via the first, second, third, and fourth opticaltransmit connections 3002 a, 3002 b, 3004 a, and 3004 b as discussedabove, as well as decode those optical signals once received asdiscussed above as well.

Thus, systems and methods have been described that include a hubIC-TROSA device with an optical directional coupler device thatsubstantially eliminates optical signal loss produced by conventionalhub IC-TROSA devices while providing dual optical receive connectionsthat allow the hub IC-TROSA device to receive two optical signals (viathe respective receive connections) from different point-to-multipointoptical networks. For example, the hub IC-TROSA point-to-multipointoptical network system of the present disclosure may include apoint-to-multipoint optical network that is coupled to subscriberdevices, and that is coupled to a hub device via a hub IC-TROSA deviceincluded in a hub coherent optical transceiver device coupled to the hubdevice. The hub IC-TROSA device includes an optical hybrid mixersubsystem, a second optical directional coupler device that is includedin the optical hybrid mixer subsystem. A first receive connection isprovided by the second optical direction coupler device, and the secondoptical directional coupler device is configured to receive a first setof optical signals at the first receive connection via thepoint-to-multipoint optical network. A second receive connection isprovided by the second optical direction coupler device, and the secondoptical directional coupler device is configured to receive a second setof optical signals at the second receive connection via thepoint-to-multipoint optical network. The optical hybrid mixer subsystemis configured to convert the first set of optical signals and the secondset of optical signals to second electrical signals and third electricalsignals, and provide the second electrical signals and third electricalsignals to the hub signal processing subsystem. As discussed above, thehub IC-TROSA device of the present disclosure increases the distanceoptical signals may be received, or increases the number of subscriberdevices to which optical signals may be received over a particulardistance, via point-to-multipoint networks relative to conventional hubIC-TROSA devices.

Although illustrative embodiments have been shown and described, a widerange of modification, change and substitution is contemplated in theforegoing disclosure and in some instances, some features of theembodiments may be employed without a corresponding use of otherfeatures. Accordingly, it is appropriate that the appended claims beconstrued broadly and in a manner consistent with the scope of theembodiments disclosed herein.

What is claimed is:
 1. An Integrated Coherent Transmit-Receive OpticalSub-Assembly (IC-TROSA) point-to-multipoint optical network system,comprising: a point-to-multipoint optical network; a plurality ofsubscriber devices that are each coupled to the point-to-multipointoptical network; a hub device; a hub coherent optical transceiver deviceincluded on the hub device; and a hub Integrated CoherentTransmit-Receive Optical Sub-Assembly (IC-TROSA) device that is includedin the hub coherent optical transceiver device and coupled to thepoint-to-point optical network to couple the hub device to the pluralityof subscriber devices, wherein the hub IC-TROSA device includes: aquadrature optical modulator subsystem; a first optical directionalcoupler device that is included in the quadrature optical modulatorsubsystem; a first transmit connection provided by the first opticaldirection coupler device, wherein the first optical directional couplerdevice is configured to receive first optical signals from thequadrature optical modulator subsystem and transmit the first opticalsignals via the first transmit connection to a first subset of theplurality of subscriber devices via the point-to-multipoint opticalnetwork; and a second transmit connection provided by the first opticaldirection coupler device, wherein the first optical directional couplerdevice is configured to receive second optical signals from thequadrature optical modulator subsystem and transmit the second opticalsignals via the second transmit connection to a second subset of theplurality of subscriber devices via the point-to-multipoint opticalnetwork.
 2. The system of claim 1, further comprising: a hub signalprocessing subsystem that is included in the hub coherent opticaltransceiver device, coupled to the quadrature optical modulatorsubsystem, and configured to transmit first electrical signals to thequadrature optical modulator subsystem that are used by the quadratureoptical modulator subsystem to generate the first optical signals andthe second optical signals.
 3. The system of claim 2, wherein the hubIC-TROSA device includes: an optical hybrid mixer subsystem; a secondoptical directional coupler device that is included in the opticalhybrid mixer subsystem; a first receive connection provided by thesecond optical direction coupler device, wherein the second opticaldirectional coupler device is configured to receive third opticalsignals at the first receive connection via the point-to-multipointoptical network; and a second receive connection provided by the secondoptical direction coupler device, wherein the second optical directionalcoupler device is configured to receive fourth optical signals at thesecond receive connection via the point-to-multipoint optical network,and wherein the optical hybrid mixer subsystem is configured to performmixing operations on the third optical signals and fourth opticalsignals and provide mixing results for conversion to second electricalsignals and third electrical signals that are then transmitted to thehub signal processing subsystem.
 4. The system of claim 3, wherein hubsignal processing subsystem is configured to: perform first signalprocessing operations on the second electrical signals and the thirdelectrical signals to identify first data included in the secondelectrical signals and the third electrical signals; and perform secondsignal processing operations that are different than the first signalprocessing operations on the second electrical signals and the thirdelectrical signals to identify second data included in the secondelectrical signals and the third electrical signals.
 5. The system ofclaim 2, wherein the hub IC-TROSA device includes: an optical hybridmixer subsystem; a MultiMode Interference (MMI) device that is includedin the optical hybrid mixer subsystem; a first receive connectionprovided by the MMI device, wherein the MMI device is configured toreceive third optical signals at the first receive connection via thepoint-to-multipoint optical network; and a second receive connectionprovided by the MMI device, wherein the MMI device is configured toreceive fourth optical signals at the second receive connection via thepoint-to-multipoint optical network, wherein the optical hybrid mixersubsystem is configured to perform mixing operations on the thirdoptical signals and fourth optical signals and provide mixing resultsfor conversion to second electrical signals and third electrical signalsthat are then transmitted to the hub signal processing subsystem.
 6. Thesystem of claim 5, wherein hub signal processing subsystem is configuredto: perform first signal processing operations on the second electricalsignals and the third electrical signals to identify first data includedin the second electrical signals and the third electrical signals; andperform second signal processing operations that are different than thefirst signal processing operations on the second electrical signals andthe third electrical signals to identify second data included in thesecond electrical signals and the third electrical signals.
 7. A hubcoherent optical transceiver device, comprising: a quadrature opticalmodulator subsystem; a first optical directional coupler device that isincluded in the quadrature optical modulator subsystem; a first transmitconnection provided by the first optical direction coupler device,wherein the first optical directional coupler device is configured toreceive first optical signals from the quadrature optical modulatorsubsystem and transmit the first optical signals via the first transmitconnection to a first subset of the plurality of subscriber devices viathe point-to-multipoint optical network; and a second transmitconnection provided by the first optical direction coupler device,wherein the first optical directional coupler device is configured toreceive second optical signals from the quadrature optical modulatorsubsystem and transmit the second optical signals via the secondtransmit connection to a second subset of the plurality of subscriberdevices via the point-to-multipoint optical network.
 8. The hub coherentoptical transceiver device of claim 7, further comprising: a hub signalprocessing subsystem that is coupled to the quadrature optical modulatorsubsystem and that is configured to transmit first electrical signals tothe quadrature optical modulator subsystem that are used by thequadrature optical modulator subsystem to generate the first opticalsignals and the second optical signals.
 9. The hub coherent opticaltransceiver device of claim 8, further comprising: an optical hybridmixer subsystem; a second optical directional coupler device that isincluded in the optical hybrid mixer subsystem; a first receiveconnection provided by the second optical direction coupler device,wherein the second optical directional coupler device is configured toreceive third optical signals at the first receive connection via thepoint-to-multipoint optical network; and a second receive connectionprovided by the second optical direction coupler device, wherein thesecond optical directional coupler device is configured to receivefourth optical signals at the second receive connection via thepoint-to-multipoint optical network, and wherein the optical hybridmixer subsystem is configured to perform mixing operations on the thirdoptical signals and fourth optical signals and provide mixing resultsfor conversion to second electrical signals and third electrical signalsthat are then transmitted to the hub signal processing subsystem. 10.The hub coherent optical transceiver device of claim 9, wherein hubsignal processing subsystem is configured to: perform first signalprocessing operations on the second electrical signals and the thirdelectrical signals to identify first data included in the secondelectrical signals and the third electrical signals; and perform secondsignal processing operations that are different than the first signalprocessing operations on the second electrical signals and the thirdelectrical signals to identify second data included in the secondelectrical signals and the third electrical signals.
 11. The hubcoherent optical transceiver device of claim 8, further comprising: anoptical hybrid mixer subsystem; a MultiMode Interference (MMI) devicethat is included in the optical hybrid mixer subsystem; a first receiveconnection provided by the MMI device, wherein the MMI device isconfigured to receive third optical signals at the first receiveconnection via the point-to-multipoint optical network; and a secondreceive connection provided by the MMI device, wherein the MMI device isconfigured to receive fourth optical signals at the second receiveconnection via the point-to-multipoint optical network, wherein theoptical hybrid mixer subsystem is configured to perform mixingoperations on the third optical signals and fourth optical signals andprovide mixing results for conversion to second electrical signals andthird electrical signals that are then transmitted to the hub signalprocessing subsystem.
 12. The hub coherent optical transceiver device ofclaim 7, wherein hub signal processing subsystem is configured to:perform first signal processing operations on the second electricalsignals and the third electrical signals to identify first data includedin the second electrical signals and the third electrical signals; andperform second signal processing operations that are different than thefirst signal processing operations on the second electrical signals andthe third electrical signals to identify second data included in thesecond electrical signals and the third electrical signals.
 13. TheIC-TROSA device of claim 7, wherein the first optical signals receivedfrom the quadrature optical modulator subsystem include a firstquadrature and a second quadrature in a first optical phaserelationship, and wherein the second optical signals received from thequadrature optical modulator subsystem include the first quadrature andthe second quadrature in a second optical phase relationship that isdifferent than the first optical phase relationship.
 14. A method fortransmitting data via a point-to-multipoint optical network, comprising:receiving, by a first optical directional coupler device included in aquadrature optical modulator subsystem in a hub Integrated CoherentTransmit-Receive Optical Sub-Assembly (IC-TROSA) device, first opticalsignals from the quadrature optical modulator subsystem; transmitting,by the first optical directional coupler device, the first opticalsignals via a first transmit connection provided by the first opticaldirectional coupler device and to a first subset of a plurality ofsubscriber devices via a point-to-multipoint optical network; receiving,by the first optical directional coupler device, second optical signalsfrom the quadrature optical modulator subsystem; and transmitting, bythe first optical directional coupler device, the second optical signalsvia a second transmit connection provided by the first opticaldirectional coupler device and to a second subset of the plurality ofsubscriber devices via the point-to-multipoint optical network.
 15. Themethod of claim 14, further comprising: transmitting, by a hub signalprocessing subsystem that is coupled to the quadrature optical modulatorsubsystem, first electrical signals to the quadrature optical modulatorsubsystem that are used by the quadrature optical modulator subsystem togenerate the first optical signals and the second optical signals. 16.The method of claim 15, further comprising: receiving, by a firstreceive connection on a second optical directional coupler deviceincluded in an optical hybrid mixer subsystem in the hub IC-TROSAdevice, third optical signals via the point-to-multipoint opticalnetwork; and receiving, by a second receive connection on the secondoptical directional coupler device included in the optical hybrid mixersubsystem in the hub IC-TROSA device, fourth optical signals via thepoint-to-multipoint optical network; and mixing, by the optical hybridmixer subsystem, the third optical signals and fourth optical signals toprovide mixing results for conversion to second electrical signals andthird electrical signals that are then transmitted to the hub signalprocessing subsystem.
 17. The method of claim 16, further comprising:performing, by the hub signal processing subsystem, first signalprocessing operations on the second electrical signals and the thirdelectrical signals to identify first data included in the secondelectrical signals and the third electrical signals; and performing, bythe hub signal processing subsystem, second signal processing operationsthat are different than the first signal processing operations on thesecond electrical signals and the third electrical signals to identifysecond data included in the second electrical signals and the thirdelectrical signals.
 18. The method of claim 15, further comprising:receiving, by a first receive connection on a MultiMode Interference(MMI) device included in an optical hybrid mixer subsystem in the hubIC-TROSA device, third optical signals via the point-to-multipointoptical network; and receiving, by a second receive connection on theMMI device included in the optical hybrid mixer subsystem in the hubIC-TROSA device, fourth optical signals via the point-to-multipointoptical network; and mixing, by the optical hybrid mixer subsystem thethird optical signals and fourth optical signals to provide mixingresults for conversion to second electrical signals and third electricalsignals that are then transmitted to the hub signal processingsubsystem.
 19. The method of claim 18, further comprising: performing,by the hub signal processing subsystem, first signal processingoperations on the second electrical signals and the third electricalsignals to identify first data included in the second electrical signalsand the third electrical signals; and performing, by the hub signalprocessing subsystem, second signal processing operations that aredifferent than the first signal processing operations on the secondelectrical signals and the third electrical signals to identify seconddata included in the second electrical signals and the third electricalsignals.
 20. The method of claim 14, wherein the first optical signalsreceived from the quadrature optical modulator subsystem include a firstquadrature and a second quadrature in a first optical phaserelationship, and wherein the second optical signals received from thequadrature optical modulator subsystem include the first quadrature andthe second quadrature in a second optical phase relationship that isdifferent than the first optical phase relationship.